EFFECT OF CURING TEMPERATURE ON THE APARUPA PANI

EFFECT OF CURING TEMPERATURE ON THE  APARUPA PANI
EFFECT OF CURING TEMPERATURE ON THE
STRENGTH OF LIME STABILIZED FLY ASH
A Thesis Submitted in Partial Fulfillment of the Requirements for the
Degree of
Master of Technology
In
Civil Engineering
APARUPA PANI
DEPARTMENT OF CIVIL ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA
2014
EFFECT OF CURING TEMPERATURE ON THE
STRENGTH OF LIME STABILIZED FLY ASH
A thesis
Submitted by
Aparupa Pani
(212CE1478)
In partial fulfillment of the requirements
For the award of the degree of
Master of Technology
In
Civil Engineering
(Geotechnical Engineering)
Under The Guidance of
Prof. S.P.Singh
Department of Civil Engineering
National Institute of Technology Rourkela
Orissa -769008, India
May 2014
NATIONAL INSTITUTE OF TECHNOLOGY ROURKELA,
ORISSA -769008, INDIA
This is to certify that the thesis entitled, “Effect of Curing Temperature on the Strength of
Lime Stabilized Fly Ash” submitted by Aparupa Pani in partial fulfillment of the requirement
for the award of Master of Technology degree in Civil Engineering with specialization in
Geotechnical Engineering at the National Institute of Technology Rourkela is an authentic
work carried out by her under our supervision and guidance. To the best of our knowledge, the
matter embodied in the thesis has not been submitted to any other University/Institute for the
award of any degree or diploma.
Place: Rourkela
Research Guide
Date:
Dr. S.P. Singh
Professor
National Institute of Technology
Rourkela
ACKNOWLEDGEMENT
First and foremost, I am glad and thankful to God for the blessing that has
given upon me in all my endeavors.
I am deeply indebted to Dr. S.P. Singh Professor of Geotechnical Engineering
specialization, my supervisor, for the motivation, guidance and patience
throughout the research work. I appreciate his broad range of expertise and
attention to detail, as well as the constant encouragement he has given me
over the years.
I am grateful to Prof. N Roy, Head of the Department of Civil Engineering
for his valuable suggestions during the synopsis meeting and necessary
facilities for the research work. And also i am sincerely thankful to Prof.
C.R. Patra and Prof. S.K.Das for their kind cooperation and necessary
advice.
I would like to thank my parents, and family members. Without their love,
patience and support, I could not have completed this work. Finally, I wish
to thank co-workers of Geotechnical lab specially Narayan Mohanty and
Dilip Das. I would like to thank many friends especially, Ellora, Mona,
Abinash and preety for the giving me support and encouragement during
these difficult years,
Aparupa Pani
Table of Contents
List of figures……………………………………………………………………………….………………………………………….vii
List of tables……………………………………………………………………….….………………………………………………..ix
List of symbols………………………………………………………………………………………………………………………….x
Abstract…………………………………………………………………………………………………………………………………..xii
CHAPTER-1 INTRODUCTION
1.1
Introduction................................................................................................................................. 1
1.2
Fly Ash: An Overview ................................................................................................................... 2
1.3
Classification of Fly Ash ................................................................................................................ 3
1.4
Impact of Fly Ash on Environment................................................................................................ 4
1.5
Strength Characteristic of Fly Ash ................................................................................................. 5
1.6
Lime: An Overview ....................................................................................................................... 6
1.7
Issues for the Millennium ............................................................................................................. 7
1.8
Use of Fly ash ............................................................................................................................... 8
CHAPTER-2 LITERETURE REVIEW AND SCOPE OF THE WORK
2.1
Introduction................................................................................................................................. 9
2.2
Literatures on Coal Ash and Its Geo-Engineering Properties ....................................................... 10
2.3
Literature on Stabilized Flyash ................................................................................................... 14
2.4
Literature on Curing Temperature.............................................................................................. 16
CHAPTER-3 EXPERIMENTAL PROGAMME
3.1
Introduction............................................................................................................................... 19
3.2
Experimental Arrangements ...................................................................................................... 19
3.2.1
Materials Used ....................................................................................................................... 19
3.2.1.1
Fly Ash ................................................................................................................................... 19
3.2.1.2
Lime ....................................................................................................................................... 20
3.2.1.3
Chemical composition of flyash .............................................................................................. 22
3.3
Determination of Index Properties ............................................................................................. 22
3.3.1
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Determination of Specific Gravity ........................................................................................... 22
3.3.2
3.4
Determination of Grain Size Distribution ................................................................................ 22
Determination of Engineering Properties ................................................................................... 23
3.4.1
Moisture Content Dry Density Relationship ............................................................................ 23
3.4.2
Determination of Unconfined Compressive Strength.............................................................. 23
3.4.3
Determination of California Bearing Ratio .............................................................................. 30
3.4.4
Determination of Permeability ............................................................................................... 33
CHAPTER-4 RESULT AND DISCUSSION
4.1
General ...................................................................................................................................... 36
4.2
Index Properties......................................................................................................................... 36
4.2.1
Specific Gravity ...................................................................................................................... 36
4.2.2
Grain Size Distribution............................................................................................................ 37
4.3
Engineering Properties ............................................................................................................... 37
4.3.1
Compaction Characteristics .................................................................................................... 37
4.3.2
Determination of Unconfined Compressive Strength.............................................................. 40
4.3.2.1
Effect of Curing condition on lime stabilized flyash ................................................................. 40
4.3.3
Determination of CBR value ................................................................................................... 66
4.3.4
Permeability characteristics ................................................................................................... 71
CHAPTER-5 CONCLUSION
5.1
Conclusions ............................................................................................................................... 72
5.2
Future Work .............................................................................................................................. 75
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Table of Figures
Title
Page No
Fig 1.1 Wet disposal of flyash ........................................................................................................ 2
Fig 1.2 Dry disposal of flyash ......................................................................................................... 2
Fig.3.1: Fly ash ............................................................................................................................. 20
Fig.3.2: Lime................................................................................................................................. 20
Physical Properties of fly ash ........................................................................................................ 20
Fig.3.3: Scanning Electron Micrograph (SEM) of flyash ............................................................. 21
Fig 3.5: before testing of (UCS sample) ....................................................................................... 25
Fig 3.6 after testing (UCS sample) ............................................................................................... 25
Fig 3.7: Lime treated fly ash sample subjected to 3 days and 26 days of curing period .............. 31
Fig 3.8: testing of CBR ................................................................................................................. 31
Fig 3.9 cured permeability samples……………………………………………………………...32
Fig 3.10: constant head permeability test ..................................................................................... 34
Fig.4.1 Grain size distribution curve of fly ash. ........................................................................... 37
Fig.4.2: Variation of dry density with moisture content of flyash at compaction energy 595kJ/m3
and 2483 kJ/m3. ............................................................................................................................ 38
Fig 4.3 Compaction characteristics of flyash amended with lime at compactive energy 595 kJ/m3
....................................................................................................................................................... 38
Fig 4.4 Compaction characteristics of flyash amended with lime at ............................................ 39
Fig 4.5: Variation of OMC of Fly ash with different lime content and compaction energy ........ 39
Fig 4.6 Variation of MDD of Fly ash with different lime content and compaction energy ......... 39
Fig 4.7(i) - 4.7(v): Stress~strain curve of stabilized flyash prepared at compactive energy of 595
kJ/m3and cured at 10°C temperature (sealed samples) ................................................................ 41
Fig4.8(i) - 4.8(v): Stress~strain curve of stabilized flyash prepared at compactive energy of 2483
kJ/m3and cured at 10°C temperature (sealed samples) ................................................................ 42
Fig 4.9(i)-4.9(v): Stress~strain curve of stabilized flyash prepared at compactive energy of 2483
kJ/m3and cured at 10°C temperature (unsealed samples) ............................................................ 43
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Fig 4.10(i) - 4.10(v): Stress~strain curve of stabilized flyash prepared at compactive energy of
595 kJ/m3and cured at 25°C temperature (sealed samples) ......................................................... 44
Fig 4.11(i)-4.11(v): Stress~strain curve of stabilized flyash prepared at compactive energy of
2483 kJ/m3and cured at 25°C temperature (sealed samples) ....................................................... 45
Fig 4.12(i)-4.12(v): Stress~strain curve of stabilized fly ash prepared at compactive energy of
2483 kJ/m3 and cured at 25°C temperature (unsealed samples) .................................................. 46
Fig 4.13 (i)-4.13(v): Stress~strain curve of stabilized fly ash prepared at compactive energy of
595 kJ/m3 and cured at 45°C temperature (sealed samples) ....................................................... 47
Fig 4.14 (i)-fig.4.14(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 2483 kJ/m3 and cured at 45°C temperature (sealed samples) .................................................. 48
Fig 4.15 (i)- Fig4.15.(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 2483 kJ/m3 and cured at 45°C temperature (unsealed samples) ............................................. 49
Fig 4.16 (i)-Fig4.16(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 595 kJ/m3 and cured at 90°C temperature (sealed samples) ................................................... 50
Fig 4.17 (i)-Fig.4.17(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 2483 kJ/m3 and cured at 90°C temperature (sealed samples) ................................................. 51
Fig 4.18(i)-Fig.4.18(v):Stress~strain curve of stabilized fly ash prepared at compactive energy of
2483 kJ/m3 and cured at temperature 90°C (unsealed samples) ................................................. 52
Fig 4.19 (i): Curing period~unconfined compressive strength curve prepared at compactive
energy 595kJ/m3 and cured at 10°C temperature (sealed samples) ............................................. 53
Fig 4.19(ii) Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 10°C temperature (sealed samples) ........................................... 53
Fig 4.19(iii) Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3and cured at 10°C temperature (unsealed samples) ........................................ 53
Fig 4.20(i): Lime content vs. unconfined compressive strength curve at compactive energy
593kJ/m3at temperature 10°C (sealed samples) ........................................................................... 54
Fig 4.20(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 10°C (sealed samples) ......................................................................... 54
Fig 4.20(iii) Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 10°C (unsealed samples) ..................................................................... 54
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Fig 4.21(i): Curing period~unconfined compressive strength curve prepared at compactive
energy 595kJ/m3 and cured at 25°C temperature (sealed samples) ............................................. 55
Fig 4.21(ii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 25°C temperature (sealed samples) ........................................... 55
Fig 4.21(iii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 25°C temperature (unsealed samples) ....................................... 55
Fig 4.22(i): Lime content vs. unconfined compressive strength curve at compactive energy
595kJ/m3at temperature 25°C (sealed samples) ........................................................................... 56
Fig 4.22(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 25°C (sealed samples) ......................................................................... 56
Fig 4.22(iii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 25°C (unsealed samples) ..................................................................... 56
Fig 4.23(i) Curing period~unconfined compressive strength curve prepared at compactive energy
595kJ/m3 and cured at 45°C temperature (sealed samples) ......................................................... 57
Fig 4.23(ii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 45°C temperature (sealed samples) ........................................... 57
Fig 4.23(iii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 45°C temperature (unsealed samples) ....................................... 57
Fig 4.24(i): Lime content vs. unconfined compressive strength curve at compactive energy
595kJ/m3at temperature 45°C (sealed samples) ........................................................................... 58
Fig 4.24(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 45°C (sealed samples) ......................................................................... 58
Fig 4.24(iii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 45°C (unsealed samples) ..................................................................... 58
Fig 4.25(i): Curing period~unconfined compressive strength curve prepared at compactive
energy 595kJ/m3 and cured at 90°C temperature (sealed samples) ............................................. 59
Fig 4.25(ii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 90°C temperature (sealed samples) ........................................... 59
Fig 4.25(iii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 0°C temperature (unsealed samples) ......................................... 59
v|Page
Fig 4.26(i): Lime content vs. unconfined compressive strength curve at compactive energy
595kJ/m3at temperature 90°C (unsealed samples) ....................................................................... 60
Fig 4.26(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 90°C (sealed samples) ......................................................................... 60
Fig 4.26(iii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 90°C (unsealed samples) ..................................................................... 60
Fig 4.27(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 0% lime(sealed samples) ......................................................................................... 61
Fig 4.27(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3 for 0% lime(sealed samples) ...................................................................................... 61
Fig 4.27(iii) Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 0% lime(unsealed samples) ................................................................................... 61
Fig 4.28(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 2% lime(sealed samples) ......................................................................................... 62
Fig 4.28(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 2% lime(sealed samples) ....................................................................................... 62
Fig 4.28(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 2% lime(unsealed samples) ................................................................................... 62
Fig 4.29(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 4% lime(sealed samples) ......................................................................................... 63
Fig 4.29(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 4% lime(sealed samples) ....................................................................................... 63
Fig 4.29(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 4% lime(unsealed samples) ................................................................................... 63
Fig 4.30(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 8% lime(sealed samples) ......................................................................................... 64
Fig 4.30(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 8% lime(sealed samples) ....................................................................................... 64
Fig 4.30(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 8% lime(sealed samples) ....................................................................................... 64
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Fig 4.31(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 12% lime(sealed samples) ....................................................................................... 65
Fig 4.31(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 12% lime(sealed samples) ..................................................................................... 65
Fig 4.31(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 12% lime(unsealed samples) ................................................................................. 65
Fig.4.32(i) Load vs penetration curve for 7days soaked CBR at 595kJ/m³ .................................. 67
Fig 4.32(ii) Load vs penetration curve for 7days soaked CBR at 2483kJ/m³ ............................... 67
Fig 4.32(iii) Load vs penetration curve for 30days soaked CBR at 595kJ/m³.............................. 67
Fig 4.32(iv) Load vs penetration curve for 30days soaked CBR at 2483kJ/m³ ............................ 68
Fig 4.32(v) Load vs penetration curve for 7days unsoaked CBR at 595kJ/m³ ............................. 68
Fig 4.32(vi) Load vs penetration curve for 7days unsoaked CBR at 2483kJ/m³ .......................... 68
Fig 4.32(vii) Load vs penetration curve for 30days unsoaked CBR at 595kJ/m³ ......................... 69
Fig 4.32(viii) Load vs penetration curve for 30days unsoaked CBR at 2483kJ/m³...................... 69
Fig 4.33(i)-4.33(ii) variation of soaked and unsoaked CBR with different lime content for 7days
curing period ................................................................................................................................. 70
Fig 4.34(i)-4.34(ii) variation of soaked and unsoaked CBR with different lime content for 30days
curing period ................................................................................................................................. 70
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List of Table
Title
Page No
Table 3.1 Physical Properties of flyash......................................................................................... 21
Table 3.2 Chemical Composition of flyash .................................................................................. 22
Table 3.3.Compaction characteristics of flyash amended with lime. ........................................... 23
Table 3.4: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 10°C (sealed samples) .............................................................. 26
Table 3.5: Unconfined compressive strength of lime-fly ash mixes compacted with 2483kJ/m3
energy and cured at temperature 10°C (sealed samples) .............................................................. 26
Table 3.6: Unconfined compressive strength of lime-fly ash mixes compacted with 2483kJ/m3
energy and cured at temperature 10°C (unsealed samples) .......................................................... 26
Table 3.7: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 25°C (sealed samples) .............................................................. 27
Table 3.8: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 25°C (sealed samples) .............................................................. 27
Table 3.9: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 25°C (unsealed samples) .......................................................... 27
Table 3.10: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 45°C (sealed samples) .............................................................. 28
Table 3.11: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 45°C (sealed samples) .............................................................. 28
Table 3.12: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 45°C (unsealed samples) .......................................................... 28
Table 3.13: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 90°C (sealed samples) .............................................................. 29
Table 3.14: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 90°C (sealed samples) .............................................................. 29
Table 3.15: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 90°C (unsealed samples) .......................................................... 29
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Table 3.16: CBR test result of Fly ash and lime treated Fly ash at 7 days of curing with
compactive energy of 595 kJ/m3 ................................................................................................... 32
Table 3.17: CBR test result of Fly ash and lime treated Fly ash at 30 days of curing with
compactive energy of 595 kJ/m3 ................................................................................................... 32
Table 3.18: CBR test result of Fly ash and lime treated Fly ash at 7days of curing with
compactive energy of 2483 kJ/m3 ................................................................................................. 32
Table 3.19: CBR test result of Fly ash and lime treated Fly ash at 30 days of curing with
compactive energy of 2483 kJ/m3 ................................................................................................. 33
Table 3.20: Co-efficient of permeability of lime stabilized flyash with different curing period at
compactive energy 593kJ/m3 and 2483kJ/m3................................................................................ 35
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LIST OF SYMBOLS
Notation
Description
E
Compaction Energy, kJ/m3
OMC
Optimum Moisture Content, %
MDD
Maximum Dry Density, kN/m3;
UCS
Unconfined Compressive Strength, kN/m3
FS
Failure Strain, %
MC
Moisture Content, %
CBR
California Bearing Ratio, %
Cu
Coefficient of uniformity
Cc
Coefficient of uniformity
G
Specific Gravity
k
coefficient of permeability, cm/sec
x|Page
ABSTRACT
In India major source of power generation is coal based thermal power plants .where 57% of the
total power generated is from coal-based thermal power plant. High ash content is found to be in
range of 30% to 50% in Indian coal. The quantum of Fly Ash produced depends on the quality of
coal used and the operating conditions of thermal power plants. Presently the annual production
of Fly Ash in India is about 112 million tonnes with 65000 acre of land being occupied by ash
ponds and is expected to cross 225 million tonnes by the year 2017. Such a huge quantity does
cause challenging problems, in the form of land usage, health hazards and environmental
dangers. Both in disposal as well as in utilization, utmost care has to be taken to safeguard the
interest of human life, wild life and environment.
Fly ash is generally classified into two types; Class C and Class F. Class C fly ash
contains high calcium content which is highly reactive with water even in absence of lime. Class
F ash contains lower percentage of lime. The main work carried out is to investigate the
suitability of class F fly ash, containing CaO as low as 1.4%, modified with added lime as a
construction material in different civil engineering fields.
These waste products are generally toxic in nature, easily ignitable, corrosive and reactive
easily and therefore cause detrimental effects on the environment. Fly Ash particles ranging in
size from 0.5 to 300 micron in equivalent diameter, being light weight, have potential to get
airborne easily and pollute the environment. If not managed properly Fly Ash disposal in
sea/rivers/ponds can cause damage to aquatic life also. Slurry disposal lagoons/ settling tanks can
become breeding grounds for mosquitoes and bacteria. It can also contaminate the under-ground
water resources with traces of toxic metals present in it.
Thus disposal of these wastes properly is one of the major concerns to be dealt with in the
present generation. An innovative solution which would be effective, efficient and
environmentally approved is required to overcome this problem of disposal. So with proper
treatment the wastes can be used in many construction aspect like construction of highways,
embankments etc.
For popularizing the usage of fly ash as one of the dominant construction material, it is
advisable to enhance and improve some properties of it by stabilizing it by addition of some
xi | P a g e
suitable stabilizer like lime. This project work aims at evaluation of the effectiveness of addition
of lime as an agent in stabilizing the waste product like fly ash and its suitability to be used as a
construction material for structural fills and embankment materials. Fly ash used for
experimentation in this project was collected from the thermal power plant of CPP- NSPCL,
Rourkela Steel Plant .For evaluating the suitability of any construction material for various
geotechnical engineering works its consistency properties, compaction properties, strength
parameters and settlement properties are the most important properties to be tested.
In this project, an attempt was made to evaluate the above stated geo-engineering
properties of fly ash along with the treated fly ash with different proportion of lime. The overall
testing program was conducted in two phases. In the first phase, the physical, chemical and
engineering properties of the fly ash samples were studied by conducting Hydrometer analysis,
light and heavy compaction test, UCS test, Permeability test and CBR test. In the second phase
of the test program, fly ash was mixed with 2%, 4%, 8% and 12% of lime as a percentage of dry
weight of Fly ash. The particular UCS ( sealed and unsealed)samples were cured for 7, 15, 30,
and 60 days with varying temperature of 10°C, 25°C, 45°C and 90°C respectively with
compactive energy 595 kJ/m3 to 2483 kJ/m3 to evaluate the effect of curing temperature on
strength of lime stabilized flyash. Sealed samples were coated with wax for 10°C, 25°C, 45°C
temperature and for higher temperature the sealed samples were coated with heat resistant
polythene cover for preventing the UCS samples from outer moisture. Then comparison study
has been done between sealed and unsealed samples. Then to study the effect of curing period on
CBR value stabilized Fly ash samples were made with different percentage of lime (0%, 2%, 4%,
8%, and 12%) at a MDD and OMC corresponding to the compaction energy of 593 and 2483 kJ/m3
and these samples were cured for 7 days and 30 days with soaking period of 4 days for soaked
samples. Comparison study has been done between soaked and unsoaked CBR with varying
compactive energy and curing period simultaneously.
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INTRODUCTION
CHAPTER 1
1.1
Introduction
Fly Ash is a by-product material generated by thermal power plants from combustion of
Pulverized coal. This is a fine residue produced from the burnt coal is carried in the flue gas,
separated by electrostatic precipitators, and collected in a field of hoppers. This residue which is
collected is called as fly ash and is considered to be an industrial waste which can be used in the
construction industry. Fly ash is one of the major industrial wastes used as a construction
material. The fly ash can either be disposed of in the dry form or the wet method in which it can
also be mixed with water and discharged as slurry into locations called ash ponds. Disposal of
residual waste is one of the greatest challenges faced by the manufacturing industries in India.
In many countries, including India, coal is used as a primary fuel in thermal power
stations and in other industries. Four countries, namely, China, India, Poland, and the United
States, together produce more than 270 million tonnes of fly ash every year and less than half of
it is used. The coal reserve of India is approximately 200 billion tonnes and its annual production
reaches 250 million tones approximately. Unlike the developed countries, in India, the ash
content present in the coal which is used for power generation is about 30-40%. The generation
of ash has increased to about 131 million tonne during 2010-11 and is expected to grow further.
In India major source of power generation is coal based thermal power plants .where
about 57% of the total power obtained is from coal-based thermal power plant. High ash content
is found to be in range of 30% to 50% in Indian coal. The quantum of Fly Ash produced depends
on the quality of coal used and the operating conditions of thermal power plants. Presently the
annual production of Fly Ash in India is about 112 million tonnes with 65000 acre of land being
occupied by ash ponds and is expected to cross 225 million tonnes by the year 2017. Such a huge
quantity does cause challenging problems, in the form of land usage, health hazards and
environmental dangers. Both in disposal as well as in utilization, utmost care has to be taken to
1|Page
INTRODUCTION
safeguard the interest of human life, wild life and environment. When pulverized coal is burnt to
generate heat, the residue contains 80% Fly Ash and 20% bottom ash.
Fig 1.1 Wet disposal of flyash
Fig 1.2 Dry disposal of flyash
1.2
Fly Ash: An Overview
Fly ash is a fine powdery material recovered from the gases while burning coal during the
production of electricity in the thermal power stations. These micron-sized earth elements consist
primarily of silica, alumina and iron. When fly-ash is mixed with lime and water, a cementitious
compound is formed which possess the properties very similar to that of Portland cement.
Because of this similarity in properties, fly ash can be used as a great replacement for a portion
of cement in the concrete, which provides advantages in the quality. The concrete which is
2|Page
INTRODUCTION
produced with the usage of flyash is denser in nature which results in a tighter, smoother surface
with less bleeding. Fly ash concrete provides an impressive architectural benefit with expertise
textural consistency and sharper detail. Fly Ash can also be called as Coal ash, Pulverized Flue
ash, and Pozzolana. Fly ash is very similar to the volcanic ashes used in production of the earliest
known hydraulic cements which were about 2,300 years ago. Those types of cements were
produced near the small Italian town of Pozzuoli - which later inspired its name to be termed as
"pozzolan".
1.3
Classification of Fly Ash
According to ASTM C618-03(2003a) there are two major classes of fly ash which are
recognized. These two classes are dependent on the type of coal burned and are designated as:
a) Class C
b) Class F.
Class C fly ashes, containing usually more than 15% CaO are also called as high calcium
ashes, became readily available for use in concrete industry .Class C fly ashes are not only
pozzolanic in nature but are invariably self cementitious in property. Class C type of fly ash has a
presence of high calcium content which is highly reactive with water even in the absence of lime.
Class F type of fly ash is generally produced by burning anthracite or bituminous coal
contains lower percentage of lime. While Class C fly ash is generally obtained by burning subbituminous or lignite coal, at present, no appreciable amount of anthracite coal is used for
generation of power. Essentially all Class F type of fly ashes presently available is derived
basically from bituminous coal. Class F fly ashes which have calcium oxide (CaO) content less
than 6%, are designated as low calcium ashes, and are not self-hardening in nature but generally
exhibit pozzolanic properties. In these ashes unburned carbon content is more than 2% and is
determined by loss on ignition (LOI) test. Quartz, mullite and hematite are the major types of
crystalline phases identified fly ashes, which are derived from bituminous coal. Therefore, major
research concerning the usage of fly ash in cement and concrete are dealt with Class F type.
Previous research findings and majority of current industry practices have already proved that
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INTRODUCTION
satisfactory and acceptable level of concrete mix can be produced with the Class F fly ash
replacing cement weight by 15-30%. Use of Class F fly ash in general reduces quantity of water
demand as well as the heat of hydration. The Concrete produced from Class F fly ash also
exhibits the properties like improved resistance to sulphate attack and Chloride ion ingress.
The main objective is to investigate the suitability of class F type of fly ash which
contains CaO as low as 1.4%, which is then modified by adding lime as a construction material.
Utilization of Fly ash on a large scale in geotechnical constructions works would enable to
reduce the disposal problems faced by the thermal power plants mostly due to its properties
which are closely related to the natural earth material. So assessment of the nature of fly ash at
different condition is required before using it in construction domain.
1.4
Impact of Fly Ash on Environment
A huge volume of Fly Ash produced from coal-based thermal power plants may bring several
problems from environmental point of view. These waste products are generally toxic in nature,
easily ignitable, corrosive and reactive easily and therefore cause detrimental effects on the
environment. Fly Ash particles ranging in size from 0.5 to 300 micron in equivalent diameter,
being light weight, have potential to get airborne easily and pollute the environment. If not
managed properly Fly Ash disposal in sea/rivers/ponds can cause damage to aquatic life also.
Slurry disposal lagoons/ settling tanks can become breeding grounds for mosquitoes and
bacteria. It can also contaminate the under-ground water resources with traces of toxic metals
present in Fly Ash. Huge investments/ expenditures are made just to get Fly Ash out from the
thermal power plants and dump it in the ponds. If understood and managed properly, it can prove
to be a valuable resource material.
Thus disposal of these wastes properly is one of the major concerns to be dealt with in
the present generation. An innovative solution which would be effective, efficient and
environmentally approved is required to overcome this problem of disposal. One of the solutions
which are applicable is utilization of waste products from one industry as raw materials of some
other industries, and hence reducing the burden on the environment. Many industrial wastes are
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INTRODUCTION
utilized in construction industries. If this supply chain is maintained properly then it would
enable the organizations to reduce the disposal problems to a great extent. The wastes can be
used in construction of highways, embankments etc. Another problem that exists is that there no
sufficient amount of soil of desired quality which is required for the construction purposes. The
search for desired quality of soil again leads to deforestation and hence affecting soil erosion and
agriculture productivity.
Cost of increase in good quality raw materials is also increasing to a high level. So
efficient and effective utilization of the waste materials that is used as a substitute for the natural
soil would not only help to reduce the disposal problem but also enable the organizations to
preserve soil and reduce deforestation. This would be of huge benefit to the government and the
country as a whole as it would help to conserve the natural resources, reduce the volume of waste
to landfills, lower the cost of construction materials as well as the waste disposal cost.
1.5
Strength Characteristic of Flyash
For popularizing the usage of fly ash as one of the dominant construction material, it is advisable
to enhance and improve some properties of it by stabilizing it by addition of some suitable
stabilizer like lime. This project work aims at evaluation of the effectiveness of addition of lime
as an agent in stabilizing the waste product like fly ash and its suitability to be used as a
construction material for structural fills and embankment materials. Fly ash used for
experimentation in this project was collected from the thermal power plant of CPP- NSPCL,
Rourkela Steel Plant. For evaluating the suitability of any construction material for various
geotechnical engineering works its consistency properties, compaction properties, strength
parameters and settlement properties are the most important properties to be tested. In this
project, an attempt was made to evaluate the above stated geo-engineering properties of fly ash
along with the treated fly ash with different proportion of lime. The overall testing program was
conducted in two phases. In the first phase, the physical and chemical characteristics of the fly
ash samples were studied by conducting Hydrometer analysis, UCS test, Permeability test and
CBR test. In the second phase of the test program, fly ash was mixed with 2%, 4%, 8% and 12%
of lime. Lime was added as a percentage of dry weight of Fly ash. The particular UCS samples
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INTRODUCTION
were cured for 7, 15, 30, and 60 days with varying temperature of 10°C, 25°C, 45°C and 90°C
respectively to evaluate the effect of curing temperature on strength of lime stabilized flyash.
1.6
Lime: An Overview
One of the oldest developed construction material is lime i.e. CaO or Ca(OH)2, which is a
by-product of burned lime stone (CaCO3), is the oldest urbanized construction materials. Man
has been using it for more than 2000 years ago. The Romans had used soil-lime mixtures for
construction of roads purposes. However, its utility in the modern geotechnical engineering was
limited until 1945, mostly due to the lack of proper understanding of the subject. Today,
stabilization of soils or waste materials by lime is being widely used in several constructions
such as highways, slope protection, embankments, railways, airports, foundation base, canal
lining etc. This is primarily due to the ease of construction, coupled with simplicity of this
technology and mostly because it is a cheapest construction material that provides an added
attraction for the engineers. Several research works have been reported highlighting the
beneficial effect of lime in improving the performance of waste materials. With proper design
and construction techniques, lime treatment chemically transforms sustainable waste into usable
materials. Lime, either alone or in combination with other materials, can be used to treat a range
of soil types.
Stabilization using lime is a long time practice to modify the characteristics of fine
grained materials. Lime stabilization occurs in soils containing a suitable amount of clay and the
propel mineralogy to produce long-term strength; and permanent reduction in shrinking, swelling
and soil plasticity with adequate durability to resist the detrimental effects of cyclic freezing and
thawing and prolonged soaking. Lime stabilization occurs over a longer time period of “curing.”
The effects of lime stabilization are typically measured after 28 days or longer, but can be
accelerated by increasing the soil temperature during the curing period. The strength increases
with the increase in the lime content up to about optimum lime content. With further increase in
the lime content the strength remains constant and at times decreases, causing deleterious effect.
The optimum lime content up to which a given fly ash demonstrates increased strength depends
on its reactive silica and varies considerably for different fly ashes. Flyashes with insufficient
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INTRODUCTION
reactive silica show increased strength only with cement and do not generally respond well to
lime (Singh and Garg 1999; Antiohos and Tsimas 2004). The strength gained is found to depend
on curing period, compactive energy, and water content (Ghosh and Subbarao 2007)
Stabilization occurs when the proper amount of lime is added to a reactive soil.
Stabilization differs from modification in a way that a significant level of long-term strength gain
is developed through a long-term pozzolanic reaction. However, research has proven that the full
term pozzolanic reaction may continue for a very long period of time even many years as long as
enough lime is present and the pH remains high (above 10). As a result of this long-term
pozzolanic reaction, some soils can show very high strength gain when treated by lime. Very
substantial enhancements in shear strength (by a factor of 20 or more in some cases), continuous
strength gain with time even after periods of environmental or load damage (autogenously
healing) and long-term durability over decades of service even under severe environmental
conditions.
1.7
Issues for the Millennium
As per the current records, ash generation in India is approximately 112 million metric tons and
its present utilization is only about 42 million metric tons (38% of ash generated). Rest of the
unutilized ash is forced to be disposed of on to the ash ponds. Disposal of this huge amount of fly
ash faces problems of enormous land requirement, transportation, ash pond construction and also
its maintenance. Also in order to meet the rising energy demand power generating industries in
India is growing rapidly. According to the future prospects, India shall continue to depend on
coal as the prime source of energy. In India environmental issues have become a major concern
in the 21st century and hence the solid waste management for coal based thermal power plants
shall continue to be a major area of priority. In developing countries like ours, where the
problems like increasing population, scarce natural resources specifically land, increasing
urbanization and energy requirements goes side by side with the development, it is almost
impossible for power generation sector to function in isolation. So now-a- day’s use of resource
material like Fly ash became a major area of research in the construction field. The past years
have witnessed a significant growth in the technology with respect to disposal of fly ash & its
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INTRODUCTION
utilization in the country and in the next millennium fly ash in itself is going to emerge as a
major industry.
1.8
Use of Fly ash
Some of the application areas of Fly ash are given below.

Manufacture of Portland cement.

Embankments and structural fill.

Waste stabilization and solidification.

Mine reclamation.

Stabilization of soft soils.

Road sub base.

Manufacture of bricks

Aggregate.

Flow able fill.

Mineral filler in asphaltic concrete.

Application on rivers to melt ice.

Used as a sub-base product in pavement design.

Other applications include cellular concrete, geo polymers, & roofing tiles
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LITERATURE REVIEW
2.1
Introduction
The coal reserve of India is estimated to be approximately around 200 billion metric tons. Due to
this reason, around 90% of the thermal power stations in India are coal based. Total installed
capacity of electricity generation is 100,000 MW in India. Out of this, about 73% is from thermal
power generation. There are overall 85 coal based thermal and other power stations in our
country. The quality of coal found here has a low calorific value of 3,000–4,000 kcal/kg and ash
content of it is as high as 35–50%. In order to achieve the required amount of energy production,
a high coal fired rate is necessarily required, generating greater ash residue. At present, India
produces nearly about 100 million metric tons of coal ash; which is expected to get doubled in
the next decade. The most common method as we known adopted in India for the disposal of
ashes produced from burning of coal is the wet method. This method requires about 1 acre of
land for every 1 MW of installed capacity, apart from a large capital investment which is
mandated. Thus, the ash ponds occupy nearly about 26,300 ha of land in India. The utilization of
this fly ash in various industries was just mere 3% in 1994, but after growth in the realization
about the need for conservation of the environment in India it has gradually been increasing. In
1994, the Government of India had commissioned a Fly Ash Mission (FAM) with the major
objective of building belief and confidence among the producers and the consumer agencies
about the safe disposal and utilization of fly ash, through technology demonstrated projects. The
Fly Ash Mission has so far chosen 10 major areas and has undertaken 55 technology
demonstration projects at 21 locations across India. The fly ash utilization has increased from 3%
in 1994 to almost 13% in 2002 which is still expected to grow even more. A notification which
was issued by the Ministry of Environment and Forests of the Government of India (MOEF
1999) on September 14, 1999, established the basic framework for the advancement in utilization
of fly ash and environment conservation efforts to be put in the country. This notification
demanded the existing thermal power plants to achieve a total of 20% utilization of fly ash
within a span of 3 years and 100% utilization within 15 years. Plants which were newly
commissioned were required to achieve 30% utilization of fly ash within the next 3 years and
100% utilization within 9 years. One of the major applications in which fly ash is demanded in
large quantities is for the construction purposes of compacted fills and embankments. According
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LITERATURE REVIEW
to the Electric Power Research Institute’s (EPRI) manual (Glogowski et al. 1992) reports, it was
stated that a project search conducted in 1984 located 33 embankments and 31 areas fills in
North America which were constructed with fly ash. The American Coal Ash Association
(ACAA 1999) reported that in 1999 about 33% of the fly ash as well as the bottom ash produced
in the United States were used in different applications. The use of fly ash in various structural
fills was its second major application (5.1%) next to its use in cement, concrete, and grout
(16.1%). Based on a survey conducted on nine thermal power stations, Porbaha et al. (2000) it
was estimated that in Japan about 41% of fly ash is used in the Landfills construction.
Considering the major role that is played by fly ash in construction of embankments and fills, the
Fly Ash Mission in India had adopted this as one of the 10 major areas for technologically
demonstrated projects. Already a few demonstrations have been made and embankments have
been constructed in India using pond ash (Vittal 2001). The Indian Road Congress had published
guidelines for the utilization of fly ash in road embankments (IRC 2001). Fly ash became an
attractive construction material because of its self-hardening characteristics which is produced by
the available free lime. The variation in its properties depends on the nature of coal, fineness of
pulverization, type of furnace used and firing temperature.
2.2
Literatures on Coal Ash and Its Geo-Engineering Properties
Many research works have been done on the properties of fly ash and pond ash by the different
researchers for study in their suitability as a construction material in various field of civil
Engineering. Some of are summarized below.
Sherwood and Ryley (1970) presented a report on self-hardening characteristics of fly ashes. He
said that the presence of free lime in the form of calcium oxide or calcium hydroxide controls the
self-hardening characteristics of fly ashes.
Gray and Lin (1972) reported a study on the variation of specific gravity of the coal ash and
they showed that the combination of many factors such as gradation, particle shape and chemical
composition is responsible for variation in specific gravity.
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Mclaren and Digioia(1987) indicated that due to the low specific gravity of coal ash as
compared to soils, low dry densities are resulting from ash fills. Because of that it can be used in
embankments on weak foundation soils, backfill material for retaining walls, , reclamation of
low-lying areas, due to which the pressure exerted on the foundation structure will be less.
Yudbir and Honjo (1991) stated that the self-hardening characteristic is developed due to the
presence of free lime content in the fly ash. Depending upon the availability of free lime and
carbon contents in the samples in the fly ash, unconfined strength may be achieved as 20
MN/m2in 28m days for some fly ash,while other attain strength in a range of 0.1-0.4 MN/m2 in
16 weeks.
Rajasekhar(1995) reported that coal ash mainly consists of glassy cenospheres and some solid
spheres . The presence of large nnumber of hollow ceno-spheres results in the variation in the
chemical composition, in particular iron content in the coal ash and also resulting in low specific
gravity of coal ash, from which the removal of entrapped air cannot be possible.
Singh (1996) studied the unconfined compressive strength of fly ashes depends upon the free
lime present within them.
Singh and Panda (1996) performed shear strength tests on freshly compacted fly ash specimens
at various water contents and concluded that most of the shear strength is due to internal friction.
Pandian and Balasubramanian (1999) showed that co-efficient of permeability of ash depend
upon the grain size ,degree of compaction and pozzolanic activity The bottom and pond ashes
being coarse grained and devoid of fines compared to fly ash have a higher value for
permeability coefficient. The consolidation pressure has negligible effect on the permeability.
Pandian(2004) tried to find out the physical, chemical and engineering properties of flyash by
conducting various laboratory experiments for characterization of flyash with reference to
geotechnical applications. He found that fly ash is a freely draining material with angle of
internal friction of more than 30 degrees with a specific gravity is lower leading to lower unit
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LITERATURE REVIEW
weights resulting in lower earth pressures. It can be summarized that fly ash (with some
modifications/additives, if required) can be effectively utilized in geotechnical applications.
Das and Yudhbir(2005) studied that the geotechnical properties of fly ashes were influenced by
the factor like lime content (Cao), iron content (Fe2O3), Loss of ignition , morphology, and
mineralogy.
Arora and Aydilek (2005) reported a study on investigation of use of classF fly ash amended
soil–cement or soil–lime as base layers in highways. A series of tests were carried out on soil–fly
ash mixtures which comprised of cement and lime as activators. The test for unconfined
compression, California bearing ratio, and resilient modulus tests were performed and he
deliberated that strength of a mixture is highly dependent on the curing period, compactive
energy, cement content, and water content at compaction.
Kim.et.al (2005) carried out number of experiments on class F flyash and bottom ash for finding
out the mechanical properties compaction, permeability, strength, stiffness, and compressibility.
they prepared Three mixtures of fly and bottom ash with different mixture ratios i.e. 50, 75, and
100% fly ash content by weight for performing the test.they found that ash mixtures posses good
agreement with the conventional granular materials. It is shown that the flyash can not only be
used as construction material such as highway embankment fillings but also it can be used as an
alternative of the traditional material.
Ghosh and Subbarao (2007) presented the shear strength characteristics of a low lime class F
fly ash modified with lime alone or in combination with gypsum. Numbers of experiments were
carried out for finding out the unconfined compression strength for both unsoaked and soaked
specimens cured up to 90 days. The gain in shear strength of modified fly ash was obtained by
adding a small percentage of gypsum 0.5 and 1.0% along with lime (4–10%) within short curing
periods 7 and 28 days. For addition of 10% lime along with 1% gypsum to the fly ash, the gain in
unsoaked unconfined compressive strength qu of the fly ash was found to be 2,853 and 3,567%,
respectively, at 28 and 90 days curing. Depending on mix proportions and curing period, there
duction of qu was varying from 30 to 2% which was the effect of 24 h soaking. Experiments
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LITERATURE REVIEW
were carried out for the measurements of unconsolidated undrained triaxial tests with porepressure for 7 and 28 days cured specimens. With addition of 10% lime along with 1% gypsum
to the fly ash the cohesion of the Class F fly ash was increased up to 3,150% and cured for 28
days. They highlighted the effects of lime content, gypsum content, and curing period on the
shear strength parameters of the fly ash. To estimate the design parameters like deviatric stress at
failure, and cohesion of the modified fly ash the empirical relationships were proposed. With this
they conclude that this modified material with improved engineering characteristics may be
helpful in different field of civil engineering.
Maitra et al. (2010) observed the reaction between fly ash and lime in fly ash–lime under water
curing and steam curing conditions. They collected the fly ash from different courses,
characterized, mixed with lime in different ratios and compacted. The compacted fly ash was
cured under both water steam condition separately. They considered the reduction in the free
CaO content in the compacted fly-ash as a function of curing lime and curing process. By
measuring the free lime content the reaction between the flyash and lime was investigated. By
determining the reaction order and rate constants with respect to the free CaO content kinetics of
these reactions was studied and it was observed that the reaction kinetics was affected by curing
conditions and additives significantly.
Reddy and Gourav(2011) examined the improvements in strength gaining characteristics of lime–
fly ash by using an additives like gypsum and under goes through low temperature steam curing.
They also discussed the influence of lime–fly ash ratio, steam curing and role of gypsum on gain
in strength, and characteristics of compacted lime–fly ash–gypsum bricks. The test result showed
that there is an increase in strength with increase in density irrespective of lime content, type of
curing and water content in the fly ash. Apart from this the results revealed that in the normal
curing conditions optimum lime–fly ash ratio yielding maximum strength is about 0.75 and at
800 C, 24 h of steam curing is sufficient to achieve nearly possible maximum strength. They even
stated that under ambient temperature conditions the pozzolanic reactions of lime take place at a
slow pace and hence it requires very long curing durations to achieve meaningful strength
values.
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LITERATURE REVIEW
Singh and Sharan (2013) showed the effect of compaction energy and degree of saturation on
strength characteristics of compacted pond ash. Here the pond ash sample was subjected to
compactive energies varying from 357 kJ/m3 to 3488 kJ/m3 which were being collected from
ash pond of Rourkela Steel Plant (RSP). By conventional compaction tests they found out The
optimum moisture content and maximum dry densities corresponding to different compactive
energies. The compaction characteristics of the specimen were assessed for different dry
densities and moisture content. They reported that by controlling the compactive energy and
moulding moisture content, the dry density and strength of the compacted pond ash can be
suitably modified. In this study they ended up with a conclusion that pond ash can replace the
natural earth materials in geotechnical constructions as the strength achieved by the pond ash in
this test was as good as a similar graded conventional earth materials.
2.3
Literature on Stabilized Flyash
Lavand and AysenLav (2000) carried out a study on micro structural, chemical, mineralogical,
and thermal analysis on fly ash as pavement base material. They stabilized the fly ash with lime
as well as with the cement separately. The stabilization effect of both lime and cement were
studied in terms of chemical composition, crystalline structures, and hydration products. They
measured the unconfined compressive strength of samples to detect the effect of stabilization
over time. The results obtained from both cement and lime stabilized samples showed that the
hydration products that account for gain in strength were almost same for both the stabilizing
agents. The proportion and density of these products are responsible for the differences in the
result on their strengths.
Ghosh and Subbarao (2001) studied the SEM (Scanning electron microscope) of modified fly
ash specimen and it was shown that a compact matrix was produced by the addition of lime to fly
ash and to achieve more compact structure as long curing period is necessary. The formation of a
densified interlocking network of reaction products is prominent for the mixes containing
gypsum, cured for 10 months at 307°C. Depending on the mix proportions and curing period the
Ca to Si ratio obtained from the EDAX analysis varies with the value ranges from 1.690 to
0.224. This variation may be accredited to the formation of different hydration products. due to
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LITERATURE REVIEW
pozzolanic reaction for the specimens stabilized with high lime (10%) and gypsum (1%) formed
a complex matrix which was cured for a longer curing period, was responsible for gaining
higher strength and durability. Due to the reduction in interconnectivity of the pore channels of
the hydration products the permeability had been reduced to 10-7 cm/s. in 3 months’ curing the
strength of fly ash, stabilized with 10% lime and 1% gypsum, had been reached a value of 6,307
kPa, i.e., 36.7 times the strength of fly ash with zero percent additive. With this they conclude
that this modified material with improved engineering characteristics may be helpful in different
field of civil engineering.
Ghosh and Subbarao (2007) studied the stabilization of low lime fly ash with lime and gypsum
through large scale tests on the stabilized material designed to simulate field recycling conditions
as thoroughly as possible. It was found to be a very effective means to control hydraulic
conductivity and leachate characteristics. They reported the effects of moulding water content,
lime content, gypsum content, curing period, and flow period on hydraulic conductivity, and on
leachate of metals flowing out of the stabilized fly ash. The values of hydraulic conductivity on
the order of 10-7 cm/s were achieved with the help of proper proportioning of the mix, and
adequate curing. The concentrations of As, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn in the
effluent emanating from the hydraulic conductivity specimens of mixes with higher proportions
of lime or lime and gypsum were found to be below threshold limits which are acceptable for
contaminants flowing into ground water.
Ali.et.al (2011)studied the effect of gypsum on the strength development of two Class F fly ashes
with different lime contents after curing them for different periods. After soaking the cured
specimens in water and with different leachates containing heavy-metal ions the sustainability of
improved strength was examined. It was seen that the strength of both the fly ash was improved
up to a particular amount of the lime content, which could be considered as optimum lime
content, and thereafter the improvement was gradual. They reported that Gypsum accelerates the
gain in strength for lime-stabilized fly ashes, particularly in the initial curing periods at about
optimum lime content. At low curing periods Gypsum helps in the improvement of reduction in
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LITERATURE REVIEW
the loss of strength due to soaking and also due to repeated cycles of wetting and drying it
improves the durability of stabilized fly ashes.
Reddy and Gourav (2011) studied the lime-pozzolana reaction required very long curing period
to achieve appreciable strength under ambient temperature conditions. He examined the
improved strength in lime–gypsum-fly ash mixes through low temperature steam curing. A
report had been presented where the results of density–strength– moulding water content
relationships, influence of lime–fly ash ratio, steam curing and role of gypsum on strength
development, and characteristics of compacted lime–fly ash–gypsum bricks were discussed and
The test results reveal that (a) strength increases with increase in density irrespective of lime
content, type of curing and moulding water content, (b) optimum lime–fly ash ratio yielding
maximum strength is about 0.75 in the normal curing conditions, (c) 24 h of steam curing (at
80_C) is sufficient to achieve nearly possible maximum strength, (d) optimum gypsum content
yielding maximum compressive strength is at 2%, (e) with gypsum additive it is possible to
obtain lime–fly ash bricks or blocks having sufficient strength ([10 MPa) at 28 days of normal
wet burlap curing.
2.4
Literature on Curing Temperature
Due to rapid industrialization the generation of fly ash goes on increasing day by day. So
disposal of this is a difficult task. Therefore it is used as an alternative of some good
conventional construction material. So it is required to know about the influencing parameters
such as temperature, moisture content chemical contents etc. of fly-ash. There are many research
works are going on effect of moisture and the chemical content present in the flyash on its
strength carrying characteristics. But there are very few surveys are done over variation of
strength with respect to temperature. So it s required to understand the effect by keeping it in
curing temperature condition. Worldwide the variation of temperature is quite high. In some
places the temperature even goes to below 00C and in some places it goes more than 500C. Few
researchers have studied the relationship between the strength and soil moisture by varying the
temperature. Similarly instead of soil we can use waste material so that it prevents the natural
resource with proper disposal of waste material .the pozzolanic reaction of fly ash is strongly
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LITERATURE REVIEW
influenced by curing temperature and replacement ratio of fly ash momentous gains in the soil
strength and modulus were only observed at the higher curing temperature of 50°C,and so it is
presumed that for any significant benefits to be gained from soil-lime stabilization work it should
be carried out in relatively hot weather. For study in their appropriateness as a construction
material in various field of civil Engineering. Few are summarized below.
George et al. (1992) found a momentous gains in the soil strength and modulus were only
observed at the higher curing temperature of 50°C, and so it is presumed that for any significant
benefits to be gained from soil-lime stabilization work it should be carried out in relatively hot
weather.
Maitra.et al. (2009) studied the hydrothermal condition for cured samples of flyash and lime .he
found that the rate of decrease in free lime content in water cured compacts was maximum up to
50–55 days of curing and in case of steam curing the rate of decrease was maximum up to a
curing period of 10 h. MgCl2 and FeCl3 were used as additives for the compacts made by
hydrothermal curing Up to a period of 4 h the additives exhibited no significant effect on the
reaction. But afterwards the additives improved the rate of reaction between fly ash and lime,
which was evident from a higher drop in free CaO content in the compacts with the additives.
MgCl2 exhibited better effect in improving the rate of reaction between fly ash and lime.
Narmluk and Nawa (2014) discussed the degree of pozzolanic reaction of fly ash cured at
different temperature .he reported the effect of curing temperature on pozzolanic reaction by
using modified Jander’s model and the results confirm that the pozzolanic reaction of fly ash is
strongly influenced by curing temperature and replacement ratio of fly ash. The higher the curing
temperature and the lower the fly ash replacement ratio, the higher is the degree of pozzolanic
reaction of fly ash. The rate and mechanism of pozzolanic reaction of fly ash vary with curing
temperature. Elevated curing temperatures lead to faster the onset and accelerated the rate of the
main reaction linearly.
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2.5
SCOPE AND OBJECTIVE OF THE PRESENT WORK
Going through the available literature it is observed that the ash production is continuing to
increase in coming years which needs large storing area creating a problem for its economical
disposal and causes associates environment hazards .A bulk utilization of flyash is only possible
in civil construction fields as a replacement to natural earth material as its properties very closely
resembles that of the natural earth. However the stabilization of ash is needed as the compacted
un-stabilized flyash is found to reduce its strength substantially on saturation. A number of
researches has already being undertaken to evaluate the effect of stabilizing agent like cement
and lime on strength properties of flyash .however the effect of curing conditions like curing
temperature, curing period and curing environment has not being addressed, upon by the
previous researchers keeping this in mind the present work aims at investigating the following
aspects of lime stabilized flyash.
 Effect of lime content and curing period on unconfined compressive strength.
 Effect of curing temperature on strength
 Effect of curing environment that is method of curing on strength.
 Effect of lime content and curing period on both soaked and unsoaked CBR values.
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EXPERIMENTAL PROGRAMME
EXPERIMENTAL PROGRAMME
3.1
Introduction
Main concern of coal based thermal power plants is Safe and economic disposal of flyash. The
problems faced by the thermal power plants for disposal of flyash can be reduced by utilizing
flyash significantly in geotechnical construction like highway and railway embankment, landfill,
road bases and sub-bases etc. construction in civil engineering field is gaining momentum as it
proves to be an effective and efficient means of bulk utilization of waste material like flyash .
However compacted ash suffers great loss of shear strength on saturation. So to transform the
waste material into safe construction material Stabilization of flyash is required .for increasing
use of flyash as a construction material, It is required to evaluate its behaviour at different
conditions and enhance some properties before using as a construction material .The tests at
laboratory scale provide a measure to control many of the variable encountered in practice as
adequate substitute for full scale field tests are not available. In the laboratory tests the trends and
behaviour pattern observed to predict the behaviour of field structures. This is helpful for
understanding the performance of the structures in the field and may be used in formulating
mathematical relationship. In the current work the effect of curing temperature on the strength of
lime stabilized flyash has been evaluated through a series of unconfined compression test,
proctor compaction and CBR tests. Details of material used, sample preparation and testing
procedure adopted have been outlined in this chapter.
3.2
Experimental Arrangements
3.2.1 Materials Used
3.2.1.1
Fly Ash
Fly ash used in this study was collected from the thermal power plant of Rourkela steel plant
(RSP).The sample was screened through 2mm sieve to separate out the foreign and vegetative
matters. The collected samples were mixed thoroughly to get the homogeneity and oven dried at
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the temperature of 105-110 degree. Then the Fly ash samples were stored in airtight container for
subsequent use.
3.2.1.2
Lime
Lime (Calcium Oxide CaO) used in this study was first sieved through 150 micron sieve and
stored in airtight container for subsequent use.
Fig.3.1: Fly ash
Fig.3.2: Lime
Physical Properties of fly ash
The physical properties of the Flyash sample passing through 2mm sieve were determined and
are presented in Tables 3.1.
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Table 3.1 Physical Properties of flyash
Physical parameters
Values
Physical parameters
Values
Colour
Light grey
Shape
Rounded/sub-rounded
Silt &clay (%)
Fine sand (%)
Medium sand (%)
88
12
0
Uniformity coefficient, Cu
Coefficient of curvature, Cc
Specific Gravity, G
5.67
1.25
2.38
Coarse sand (%)
0
Plasticity Index
Non-plastic
Fig.3.3: Scanning Electron Micrograph (SEM) of flyash
The surface morphology of flyash was studied by using Scanning Electron Microscope. This
analysis show that flyash mainly contain angular size particle and have uniform gradation.
Micrographs were taken at accelerating voltages of 20 kV for the best possible resolution. Fig
3.3 shows the surface morphology of flyash.
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3.2.1.3
Chemical composition of flyash
The chemical compositions of the flyash sample passing through 2mm sieve were determined
and are presented in Tables 3.2 and it shows that the flyash merely consists of aluminum oxide
and silicon oxide. Apart from these two major particles it contains magnesium (MgO), potassium
(K2O), calcium oxide (CaO).
Table 3.2 Chemical Composition of flyash
Loss on
Elements
MgO
Al2O3
SiO2
K 2O
P2 O 5
CaO
Fe2O3
Na2O
MnO
TiO2
Ignition
1.7
28.1
53.6
1.97
1.72
2.65
1.8
0.5
0.3
0.85
6.5
Composition
(%)
3.3
Determination of Index Properties
3.3.1
Determination of Specific Gravity
The specific gravity of flyash was determined according to IS: 2720 (Part-III, section-1) 1980 by
using Le-Chatelier flask with Kerosene as the solvent. The specific gravity of flyash was found
to be 2.38.
3.3.2
Determination of Grain Size Distribution
Flyash was passed through 75μ size opening test sieve for determination of grain size
distribution. For determination of coarser particles Sieve analysis was conducted as per IS: 2720
part (IV), 1975 and for finer particles hydrometer analysis was conducted as per IS: 2720 part
(IV). The percentage of flyash passing through 75μ sieve was found to be 88% .Hence the
particle size of flyash ranges from fine sand to silt size. Coefficient of uniformity (Cu) and
coefficient of curvature (Cc) was found to be 5.67 & 1.25respectively, indicating uniform
gradation of samples. The grain size distribution curve of flyash is presented in Fig 4.1
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3.4
Determination of Engineering Properties
3.4.1
Moisture Content Dry Density Relationship
The moisture content, dry density relationships were found by using compaction tests as per IS:
2720 (Part VII) 1980. Fly ash was stabilized with varying percentage of lime (0%, 2%, 4%, 8%
and 12%) of its dry weight. For this test, flyash was thoroughly mixed with adequate amount of
water and the wet sample was compacted in proctor mould either in three or five equal layers
using standard proctor rammer of 2.6 kg or modified proctor rammer of 4.5 kg. As per IS: 2720
(Part 2) 1973 the moisture content of the compacted mixture was determined. From the dry
density and moisture content relationship, optimum moisture content (OMC) and maximum dry
density (MDD) were determined. Similar compaction tests were conducted with varying
percentage of lime (0%, 2%, 4%, 8% and 12%) and the corresponding OMC and MDD were
determined. This was done to study the effect of lime content and compactive energy on OMC
and MDD. The compactive energies used in this test programme 595 and 2483 kJ/m3 of
compacted volume. The test results are presented in Table 3.3
Table 3.3.Compaction characteristics of flyash amended with lime.
Compactive energy at 593 kJ/m³
Lime
content (%)
0
2
4
8
12
3.4.2
Compactive energy at 2483 kJ/m³
Maximum dry
density, MDD (g/cc)
Optimum moisture
content, OMC (%)
Maximum dry density,
MDD (g/cc)
Optimum moisture
content, OMC (%)
1.12
1.085
1.089
1.097
1.108
40.5
43
42
41.5
41.3
1.236
1.206
1.237
1.244
1.25
33
35.8
35
34.8
34.5
Determination of Unconfined Compressive Strength
The Unconfined compressive strength test is one of the common tests used to study the strength
characteristics of soil and stabilized soil. For testing fly ash and lime stabilized fly ash specimens
were compacted to their corresponding MDD at OMC with compactive energy varying as 593
and 2483 kJ/m3 according to IS: 2720 (Part X). The cylindrical test specimens were of size 50
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mm in diameter and 100 mm in height were sheared at an axial strain rate of 1.25 mm/min till
failure of the sample. Samples were prepared in two ways i.e. sealed and unsealed. Sealed
samples were coated with wax to maintain the actual moisture and unsealed samples were made
without any coating to check strength variation between two. To evaluate the effects of curing
temperature on strength properties of sealed and unsealed UCS samples the specimen were cured
at a temperature of 10°C, 25°C, 45°C and 90°C with a curing periods of 0, 7, 15, 30, and 60 days
before testing . For each lime content and curing period three identical specimens were tested
and the average value was reported.
Sealed by polythene
coating (for temp.
more than 70°C)
Sealed with wax coating
(for temp. lesser than
70°C
Unsealed samples
(without any coating)
Fig 3.4: samples are cured at different temperature with wax coating
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Fig 3.5: before testing of (UCS sample)
Fig 3.6 after testing (UCS sample)
The unconfined compressive strengths of specimens were determined from stress versus strain
curves and the failure stress and corresponding failure strain at 10°C, 25°C, 45°C, and 90°C
temperature with 0, 7, 15, 30 and 60 days of curing at a compactive energy of 595 kJ/m3 and
2853 kJ/m3 is given in Table, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 3.10, 3.11, 3.12, 3.13, 3.14, and 3.15.
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Table 3.4: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 10°C (sealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
184.21
2.75
190.30
3.00
214.48
3.00
239.80
2.75
280.66
3.25
2
261.52
2.75
315.76
2.75
340.56
2.25
426.44
2.00
441.77
1.75
4
312.50
2.75
450.67
2.75
453.47
2.5
533.05
2.00
630.93
2.25
8
348.53
3.25
506.24
2.5
625.01
2.75
1117.22
2.5
1767.75
2.50
12
354.36
3.00
539.33
2.75
738.24
3.00
1739.47
2.5
2856.69
2.50
Table 3.5: Unconfined compressive strength of lime-fly ash mixes compacted with 2483kJ/m3
energy and cured at temperature 10°C (sealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
375.38
3.5
383.97
3.25
401.49
3.5
513.54
3.00
547.30
3.25
2
536.95
3.5
631.30
2.75
695.59
3.00
758.54
2.25
843.60
2.25
4
625.09
4.00
665.43
3.00
919.74
3.75
1060.65
2.5
1130.06
2.00
8
691.66
4.00
940.40
3.00
1282.66
4.00
1969.73
3.00
2121.3
2.50
12
836.66
4.5
1105.15
3.5
1601.59
3.75
2946.98
3.25
3723.92
2.75
Table 3.6: Unconfined compressive strength of lime-fly ash mixes compacted with 2483kJ/m3
energy and cured at temperature 10°C (unsealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
375.38
3.5
411.39
3.25
506.07
3.5
575.95
3.25
596.41
3.25
2
536.95
3.5
767.93
3.25
770.67
3.25
808.41
3.00
909.82
2.75
4
625.09
4.00
835.91
3.00
948.65
3.00
1086.13
3.00
1195.91
3.00
8
691.66
4.00
990.26
3.5
1371.31
3.25
2136.26
4.00
2532.51
3.00
12
836.66
4.5
1148.92
3.5
1691.63
3.75
3367.97
3.25
4556.16
2.75
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Table 3.7: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 25°C (sealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
190.21
2.75
200.94
2.5
222.21
2.5
272.56
3.00
307.97
3.00
2
290.60
2.5
355.36
2.25
371.30
2.00
443.14
2.25
450.34
2.75
4
320.5
2.75
465.70
2.00
472.35
2.00
550.26
2.75
648.93
3.00
8
360.53
3.25
829.16
2.25
1155.30
2.5
1215.74
2.75
1777.75
3.25
12
372.35
3.00
1209.87
2.75
1885.64
2.75
2207.80
3.25
3077.45
2.00
Table 3.8: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 25°C (sealed samples)
Lime
content
(%)
0
2
4
8
12
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
395.57
551.84
639.09
712.12
860.65
3.25
3.25
3.5
4.00
4.5
406.96
694.43
860.117
1541.57
2032.69
3.00
2.75
2.75
3.75
3.75
412.17
750.66
968.73
1694.30
2475.16
3.25
3.25
2.5
2.25
2.00
530.20
800.06
1100.81
2019.04
3475.16
3.75
3.25
3.75
3.5
2.75
550.94
850.60
1160.81
2379.91
4408.05
3.00
2.5
2.5
3.25
2.5
Table 3.9: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 25°C (unsealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
395.57
3.5
426.20
3.00
493.46
2.75
588.90
2.5
610.81
2.75
2
551.84
3.25
785.43
3.75
792.85
3.25
800.06
3.00
990.82
3
4
639.09
3.5
860.11
2.75
970.67
3.00
832.24
2.5
1200.90
2.75
8
712.12
4.00
1392.99
2.5
1779.30
3.25
1165.81
2.25
2220.95
3.5
12
860.65
4.25
1866.75
2.5
2220.95
4.00
2195.40
2.25
4558.15
3.00
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Table 3.10: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 45°C (sealed samples)
ime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
195.64
2.75
205.64
2.5
224.21
2.5
291.26
2.5
310.96
3.00
2
290.84
2.75
361.43
2.25
373.36
2.00
443.14
2.25
453.93
2.75
4
322.50
2.75
469.48
2.00
480.35
2.25
594.23
3.00
655.03
3.00
8
364.80
3.25
974.79
2.25
1188.46
2.5
1297.67
3.00
1891.15
2.75
12
384.94
3.00
1654.07
2.5
2131.02
3.00
3181.95
2.5
2900.93
3.00
Table 3.11: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 45°C (sealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
395.57
3.75
410.95
3.00
413.18
3.5
535.2
3.75
560.94
3.25
2
551.84
3.75
696.43
2.75
755.86
3.25
805.01
3.25
860.94
3.00
4
639.09
3.75
862.43
2.75
972.82
3.00
1188.55
4.00
1814.34
3.25
8
712.12
4.25
1167.77
3.00
2877.21
3.00
3167.81
2.5
3462.96
2.75
12
860.65
4.75
3266.80
2.5
3402.79
2.25
3575.80
3.25
4513.84
2.75
Table 3.12: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 45°C (unsealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
395.57
3.5
428.95
3.00
519.07
3.5
589.0
3.75
612.00
3.25
2
551.84
3.5
788.84
3.00
798.30
3.5
835.0
3.25
992.48
2.25
4
639.09
3.5
879.90
3.00
992.48
2.25
1192.56
3.00
1914.34
3.25
8
712.12
3.75
1870.46
3.25
2286.43
3.75
3296.26
2.5
3496.27
3.00
12
860.65
4.25
3582.86
2.75
4678.10
3.00
5472.81
3.25
7294.47
3.75
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Table 3.13: Unconfined compressive strength of lime-fly ash mixes compacted with 595 kJ/m3
energy and cured at temperature 90°C (sealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
195.64
2.75
248.11
2.75
319.79
2.75
343.71
3.00
355.18
3.25
2
290.84
2.75
363.11
2.5
379.88
2.00
448.81
2.25
460.98
2.5
4
322.50
2.75
621.08
1.75
647.28
2.00
682.36
1.75
713.96
2.00
8
364.80
3.25
2191.64
2.75
2273.87
2.00
2304.27
2.00
2460.98
2.75
12
384.94
3.00
4041.51
2.25
4475.83
2.25
5479.07
2.00
5951.39
3.00
Table 3.14: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 90°C (sealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
395.57
3.5
523.79
2.75
514.19
3.00
580.2
3.00
606.49
2.75
2
551.84
3.5
698.48
2.75
800.86
3.25
850.10
3.25
905.94
2.25
4
639.09
3.5
1151.96
1.75
1366.60
3.00
1416.09
3.00
1900.15
3.25
8
712.12
3.75
3965.18
1.75
4535.65
2.00
4708.15
3.00
5066.97
2.25
12
860.65
4.25
6925.67
3.25
7280.19
2.5
7905.92
2.5
8396.44
3.75
Table 3.15: Unconfined compressive strength of lime-fly ash mixes compacted with 2483 kJ/m3
energy and cured at temperature 90°C (unsealed samples)
Lime
content
(%)
Immediate
7days
15 days
30 days
60 days
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
Failure
stress(σ)
in kPa
Failure
strain(ε)
in %
0
395.57
3.5
474.90
3.00
520.60
3.00
590.8
3.00
625.32
2.75
2
551.84
3.5
790.50
3.00
805.32
3.25
860.31
3.25
999.30
2.25
4
639.09
3.5
1182.82
1.75
1400.98
3.00
1499.79
2.00
1932.83
3.25
8
712.12
3.75
4312.30
3.00
4793.96
3.25
5103.17
2.25
5139.36
2.25
12
860.65
4.25
7052.73
4.00
7295.74
2.5
9206.36
3.25
9813.80
3.5
29 | P a g e
EXPERIMENTAL PROGRAMME
3.4.3
Determination of California Bearing Ratio
One of the essential parameter, used in the evaluation of soil sub grades for both rigid and flexible
pavement design is bearing ratio. It is also a primary part of numerous pavement thickness design
Methods. To evaluate the suitability of Fly ash and lime-stabilized flyash both in soaked and
unsoaked condition, the CBR tests have been conducted in accordance with IS: 2720(Part XVI)1987. For this test specimens were prepared in a rigid metallic cylindrical mould with an inside
diameter of 150 mm and a height of 175 mm to their MDD at OMC. Static compaction is done by
keeping the mould assembly in compression machine and compacted the sample by pressing the
displacer disc till the level of the disc reaches the top of the mould. The load was kept for some time,
and then release. The displacer disc was removed .The mould with samples were tested in a CBR
testing machine. A mechanical loading machine equipped with a movable base that moves at a
uniform rate of 1.2 mm/min and a calibrated proving ring is used to record the load. The proving ring
is attached with a piston, which penetrates into the compacted specimen. Diameter of the piston is 50
mm .The load was recorded carefully as function of penetration up to a penetration of 12.5 mm.
To study the effect of curing period the fly ash and lime stabilized Fly ash
samples with different percentage of lime (0%, 2%, 4%, 8%, and 12%) were prepared at a MDD and
OMC corresponding to the compaction energy of 593 and 2483 kJ/m3.To study the effect of
pozzolanic reaction of lime on CBR value of stabilized fly ash these samples were subjected to a
curing period of 7 days and 30 days for a soaking period of 4 days for soaked samples as shown in
figure 3.7(i)-3.7(ii).
Fig 3.7(i): Lime treated fly ash sample subjected to 7 days of curing period
30 | P a g e
EXPERIMENTAL PROGRAMME
Fig 3.7(ii): Lime treated fly ash sample subjected to 30 days of curing period
Fig 3.8: testing of CBR
The Soaked and unsoaked CBR value of all samples at different compaction energy are given in the
table 3.16, 3.17, 3.18 and 3.19.
31 | P a g e
EXPERIMENTAL PROGRAMME
Table 3.16: CBR test result of Fly ash and lime treated Fly ash at 7 days of curing with
compactive energy of 595 kJ/m3
Lime content in %
0
2
4
8
12
Soaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration (%)
1.3
33.9
39.3
44.2
53.4
1.2
32.3
38.8
43.9
51.8
Unsoaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration(%)
24.89
38.8
41.27
55.03
63.93
24.53
38.5
41.00
52.33
62.04
Table 3.17: CBR test result of Fly ash and lime treated Fly ash at 30 days of curing with
compactive energy of 595 kJ/m3
Lime content in %
0
2
4
8
12
Soaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration (%)
2.5
44.5
61.5
117.4
165.1
2.4
43.2
59.9
112.8
162.4
Unsoaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration(%)
26.71
45.32
63.13
121.40
180.48
25.90
42.08
57.73
113.30
174.27
Table 3.18: CBR test result of Fly ash and lime treated Fly ash at 7days of curing with
compactive energy of 2483 kJ/m3
Lime content in %
0
2
4
8
12
32 | P a g e
Soaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration (%)
5.8
86.6
105.2
109.3
113.3
5.7
83.1
104.1
105.2
108.4
Unsoaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration(%)
72.8
91.5
110.1
118.2
135.2
71.2
87.4
105.2
109.0
133.8
EXPERIMENTAL PROGRAMME
Table 3.19: CBR test result of Fly ash and lime treated Fly ash at 30 days of curing with
compactive energy of 2483 kJ/m3
Lime content in %
0
2
4
8
12
3.4.4
Soaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration (%)
12.1
89.0
128.7
153.0
279.2
11.3
80.9
121.9
151.6
262.8
Unsoaked CBR value
CBR Value at
CBR value
2.5 mm
at 5mm
Penetration(%) Penetration(%)
75.3
95.5
139.2
195.9
290.5
74.5
90.6
136.5
194.8
288.7
Determination of Permeability
The permeability of fly ash is determined according to IS: 2720 (Part XVII)-1986. For evaluating
hydraulic conductivity, test samples were prepared corresponding to their MDD at OMC in a
permeability mould having diameter 10cm × height 12.5cm with 595 and 2483 kJ/m3 of
compaction energy. However the Lime stabilized samples was subjected to a curing period of 7
days, 15 days and 30 days at moist environment to maintaining its moisture content for proper
curing. Constant head permeability test was run and the coefficients of permeability were
determined. Values of coefficient of permeability of these samples are presented in Table. 3.20.
Fig 3.9 cured permeability samples
33 | P a g e
EXPERIMENTAL PROGRAMME
Fig 3.10: Constant head permeability test
Fig 3.11 Constant head permeameter
34 | P a g e
EXPERIMENTAL PROGRAMME
Table 3.20: Co-efficient of permeability of lime stabilized flyash with different curing period at
compactive energy 593kJ/m3 and 2483kJ/m3
Coefficient of permeability(k) at different compaction energy (cm/sec)
samples
7 day
593kJ/m3
-5
15 days
2483kJ/m3
-5
593kJ/m3
-5
FA+0%L
5.31×10
FA+2%L
4.65×10-5
FA+4%L
3.04×10
-5
1.44×10
-5
6.72×10
FA+8%L
2.26×10
-5
0.98×10
-5
2.91×10
FA+12%L
1.58 ×10
-5
0.474×10
35 | P a g e
3.91×10
2.32×10-5
-5
2.5×10
2.105×10-5
30 days
2483kJ/m3
-5
-5
1.605×10
1.34×10
1.98×10-5
1.20×10-5
-6
3.97×10
-6
2.44×10
-6
1.23×10
2.01×10
593kJ/m3
2483kJ/m3
1.31×10
-5
1.16×10-5
-6
3.88×10
-6
3.67×10
-6
-6
2.42×10
-6
2.34×10
-6
-6
1.02×10
-6
1.00×10
-6
RESULTS AND DISCUSSION
RESULTS AND DISCUSSION
4.1
General
Fly ash is a fine residues generated due to combustion of coal, and comprises of very fine
particles that rise with the flue gases. This material is solidified while suspended in exhausted
and captured by electrostatic precipitators or other particle filtration equipment before the flue
gases reach the chimneys of coal fired power plants. Fly ash generally contains spherical shape
particles. Fly ash consists of inorganic matter present in the coal that has been fused during coal
combustion. On compacted fly ash specimen a series of traditional laboratory tests are being
carried out such as light and heavy compaction tests, unconfined compressive strength tests,
CBR tests and permeability test .these test results are presented and discussed in this chapter.
4.2
Index Properties
4.2.1 Specific Gravity
According to IS: 2720 (Part-III, section-1) 1980the specific gravity of fly ash was determined
and found to be 2.38guidelines by Le-Chartelier method with kerosene oil. Specific gravity is
one of the important physical properties needed for the use of coal ashes for geotechnical and
other applications. In coal ash the variation of specific gravity occurs due to combination of
many factors such as gradation, particle shape and chemical composition. The specific gravity of
fly ash is found to be lower than that of the conventional earth material and it depend on the
source of coal, degree of pulverization and firing temperature. The reason for a low specific
gravity could either be due to the presence of large number of hollow cenospheres from which
the entrapped micro bubbles of air cannot be removed, or the variation in the chemical
composition, in particular iron content, or both .In general, coal ashes having specific gravity lies
around 2.0 but it can be vary to a larger extent (1.6 to 3.1). The presence of foreign materials in
the fissures of the coal seams mostly influences the specific gravity of resulting flyash.
36 | P a g e
RESULTS AND DISCUSSION
4.2.2 Grain Size Distribution
Mostly the particles present in Fly ash ranges from fine sand to silt size as shown in Fig. 4.1. The
percentage of Fly ash passing through 75μ sieve was found to be 88%. The uniformity
coefficient (Cu) and coefficient of curvature (Cc) for Fly ash were found to be 5.67 & 1.25
respectively, indicating uniform gradation of samples. The grain size distribution mostly depends
on degree of pulverization of coal and firing temperature in boiler units. The grain size
distribution also affected due to presence of foreign matters in flyash. In ash pond the original
particles undergoes flocculation and conglomeration resulting in an increase in particle size.
Fig.4.1 Grain size distribution curve of fly ash.
4.3 Engineering Properties
4.3.1 Compaction Characteristics
The compaction characteristics of fly ash with different lime content and varying compaction
energies 593 and 2483 kJ/m³ of compacted volume have been studied. The OMC (optimum
moisture content) and MDD (maximum dry density) of fly ash and flyash amended with lime
samples corresponding to these compactive efforts have been evaluated and presented in fig 4.2,
4.3 and 4.4 .Dry density and moisture content relationship of fly ash at different lime content and
compactive energies have been shown in Fig 4.5 and Fig 4.6. It is seen that as the compactive
energy increases the MDD increases and the water required to achieve this density is reduced.
Initially the addition of lime imparts plasticity to the flyash resulting in marginal decrease in dry
37 | P a g e
RESULTS AND DISCUSSION
density and increase in moisture content values but later on due to more addition of lime results
increase in dry density and reduction in moisture content .The MDD of fly ash specimen is found
to change from 1.12 to 1.236 g/cc with change in compaction energy from 595 to 2483kJ/m3,
and 1.108 to 1.25 g/cc with lime treated flyash at similar compactive energies .whereas the OMC
of flyash and flyash amended with lime is found to decrease from 40.5to 33% and 41.3 to 34.5
respectively. This shows that the compacted density of fly ash responds very poorly to the
compaction energy. There are many factors like gradation, carbon content, iron content and
fineness etc., mainly control the compaction characteristics of fly ash.
Fig.4.2: Variation of dry density with moisture content of flyash at compaction energy 595kJ/m3
and 2483 kJ/m3.
Fig 4.3 Compaction characteristics of flyash amended with lime at compactive energy 595 kJ/m3
38 | P a g e
RESULTS AND DISCUSSION
Fig 4.4 Compaction characteristics of flyash amended with lime at compaction energy
2483 kJ/m3
Fig 4.5: Variation of OMC of Fly ash with different lime content and compaction energy
595kJ/m3
Fig 4.6 Variation of MDD of Fly ash with different lime content and compaction energy
2483kJ/m3
39 | P a g e
RESULTS AND DISCUSSION
The variation of MDD and OMC with the compaction energy and lime content is shown in figure
4.5 & 4.6.With increase in compaction energy and lime content MDD decreases& OMC
increases up to certain stage after that MDD increases and OMC decreases. A linear relationship
between OMC, MDD, lime content and compaction energy is found after compaction energy of
595 kJ/m3 and 2483 kJ/m3 with different percentage of lime.
4.3.2 Determination of Unconfined Compressive Strength
4.3.2.1
Effect of Curing condition on lime stabilized flyash
Unconfined compressive strength tests were carried out on treated fly ash specimens
compacted to their corresponding MDD at OMC with compactive effort varying as 593 and
2483kJ/m3. The stress-strain relationships of compacted fly ash with curing temperature of
10°C, 25°C, 45°C and 90°C /immediate, 7days, 15days, 30days and 60days were presented in
Fig.4.7- Fig.4.18. Form these plots it is observed that the failure stress as well as failure strain of
samples compacted with greater compaction energy, are higher than the samples compacted with
lower compaction energy. At higher temperature and curing period the unconfined compressive
strength give remarkable strength.
The immediate compressive strength of fly ash is 184.21kPa at compaction energy of 595
kJ/m³ which increases to 375.38kPa at compaction energy of 2483kJ/m³ at 10°C, similarly
immediate compressive strength of fly-ash at 90°C with similar compactive energies are
195.64kPa and 395.57kPa respectively. However in general the failure strains are found to be
lower for samples compacted with higher energies. The failure strains vary from a value of 2 to
3.75%, indicating brittle failure in the specimens. The increase in unconfined strength of
specimens with increased compactive effort is attributed to the closer packing of particles,
resulting in the increased interlocking among particles. A closer packing is also responsible in
increasing the cohesion component in the sample.
40 | P a g e
RESULTS AND DISCUSSION
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
300
200
7 days curing
600
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
500
stress in kPa
0 days curing
400
400
300
200
100
100
0
0
0
1
2
3
4
strain in %
5
6
7
0
1
2
3
4
5
strain in %
Fig 4.7(i)
7
Fig 4.7(ii)
FA+0%L
FA+2%L
600
FA+4%L
FA+8%L
400
FA+12%L
200
0
30 days curing
2000
FA+0%L
1500
stress in kPa
15 days curing
800
stress in kPa
6
FA+2%L
FA+4%L
1000
FA+8%L
FA+12%L
500
0
0
1
2
3
4
5
strain in %
6
7
0
1
Fig 4.7(iii)
2
3
4
strain in %
5
6
7
Fig 4.7(iv)
3500
60 days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
3000
2500
2000
1500
1000
500
0
0
1
2
3
4
strain in %
5
6
7
Fig 4.7(v)
Fig 4.7(i) - 4.7(v): Stress~strain curve of stabilized flyash prepared at compactive energy of 595
kJ/m3 and cured at 10°C temperature (sealed samples)
41 | P a g e
RESULTS AND DISCUSSION
0 days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
800
600
400
200
7 days curing
1200
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
1000
stress in kPa
1000
800
600
400
200
0
0
1
2
3 4 5
strain in %
6
0
7
0
1
2
3
4
5
strain in %
Fig 4.8(i)
6
7
Fig 4.8(ii)
15 days curing
1750
1500
1000
FA+8%L
750
500
stress in kPa
stress in kPa
FA+4%L
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
FA+2%L
1250
30 days curing
3500
FA+0%L
2500
2000
1500
1000
500
250
0
0
0
1
2 3 4 5
strain in %
6
0
7
1
2
3 4 5
strain in %
Fig 4.8(iii)
6
7
Fig 4.8(iv)
60 days curing
stress in kPa
4000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
2000
1000
0
0
1
2
3
4
strain in %
5
6
7
Fig 4.8(v)
Fig4.8(i) - 4.8(v): Stress~strain curve of stabilized flyash prepared at compactive energy of 2483
kJ/m3and cured at 10°C temperature (sealed samples)
42 | P a g e
RESULTS AND DISCUSSION
0 days curing
1000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
600
1000
400
800
600
400
200
200
0
0
0
1
2
3 4 5
strain in %
6
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
1200
stress in kPa
stress in kPa
800
7 days curing
1400
0
7
1
2
3
4
5
6
7
strain in %
Fig 4.9(i)
Fig 4.9(ii)
15 days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
1500
1000
30 days curing
4000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
stress in kPa
2000
2000
1000
500
0
0
0
1
2
3
4
strain in %
5
6
0
7
1
2
3
Fig 4.9(iii)
5
6
7
Fig 4.9(iv)
5000
60 days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
4000
stress in kPa
4
strain in %
3000
2000
1000
0
0
1
2
3
4
5
6
7
strain in %
Fig 4.9(v)
Fig 4.9(i)-4.9(v): Stress~strain curve of stabilized flyash prepared at compactive energy of 2483
kJ/m3and cured at 10°C temperature (unsealed samples)
43 | P a g e
0 days curing
400
350
300
250
200
150
100
50
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
7 days curing
1500
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
1250
1000
stress in kPa
stress in kPa
RESULTS AND DISCUSSION
750
500
250
0
0
1
2
3
4
strain in %
5
6
0
7
1
2
3
strain in %
Fig 4.10(i)
6
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
2000
1500
1000
500
0
30days curing
2500
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
2000
stress in kPa
stress in kPa
5
Fig 4.10(ii)
15 days curing
2500
4
1500
1000
500
0
0
1
2
3
4
5
strain in %
6
7
0
1
2
3
4
strain in %
Fig 4.10(iii)
6
7
Fig 4.10(iv)
60 days curing
3500
stress in kPa
5
3000
FA+0%L
2500
FA+2%L
2000
FA+4%L
1500
FA+8%L
1000
FA+12%L
500
0
0
1
2
3
4
strain in %
5
6
7
Fig 4.10(iv)
Fig 4.10(i) - 4.10(v): Stress~strain curve of stabilized flyash prepared at compactive energy of
595 kJ/m3and cured at 25°C temperature (sealed samples)
44 | P a g e
RESULTS AND DISCUSSION
0 days curing
1000
600
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
2000
stress in kPa
stress in kPa
800
7 days curing
2500
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
1500
1000
400
200
500
0
0
0
1
2 3 4 5
strain in %
6
0
7
1
Fig 4.11(i)
2500
6
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
2000
FA+0%L
1500
FA+2%L
1000
FA+4%L
500
FA+8%L
0
0
1
2 strain
3 in %
4
7
30 days curing
4000
stress in kPa
stress in kPa
3
4
5
strain in %
Fig 4.11(ii)
stress ~strain curve(15 days
curing)
3000
2
2000
1000
FA+12%L
5
6
7
0
0
1
Fig 4.11(iii)
2
3
4
strain in %
5
6
7
Fig 4.11(iv)
60 days curing
5000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
4000
3000
2000
1000
0
0
1
2
3
4
strain in %
5
6
7
Fig 4.11(v)
Fig 4.11(i)-4.11(v): Stress~strain curve of stabilized flyash prepared at compactive energy of
2483 kJ/m3and cured at 25°C temperature (sealed samples)
45 | P a g e
RESULTS AND DISCUSSION
600
400
stress in kPa
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
800
stress in kPa
7 days curing
0 days curing
1000
200
0
0
1
2
3 4 5
strain in %
6
2000
1750
1500
1250
1000
750
500
250
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
7
1
2
3
4
strain in %
Fig 4.12(i)
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
7
2
3
4
strain in %
5
6
7
30 days curing
stress in kPa
stress in kPa
15 days curing
1
6
Fig 4.12(iii)
3500
3000
2500
2000
1500
1000
500
0
0
5
2500
2250
2000
1750
1500
1250
1000
750
500
250
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
1
2
3
4
strain in %
Fig 4.12(iii)
5
6
7
Fig 4.12(iv)
60days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
5000
stress in kPa
4000
3000
2000
1000
0
0
1
2 strain
3 in
4% 5
6
7
Fig 4.12(v)
Fig 4.12(i)-4.12(v): Stress~strain curve of stabilized fly ash prepared at compactive energy of
2483 kJ/m3 and cured at 25°C temperature (unsealed samples)
46 | P a g e
RESULTS AND DISCUSSION
0 days curing
500
300
stress in kPa
stress in kPa
400
7days curing
2000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
200
100
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
1500
1000
500
0
0
0
1
2
3
4
strain in %
5
6
0
7
1
2
3
strain in %
15 days curing
2500
2250
2000
1750
1500
1250
1000
750
500
250
0
5
6
Fig 4.13(ii)
FA+8%L
FA+12%L
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
FA+2%L
FA+4%L
30 days curing
3500
FA+0%L
stress in kPa
stress in kPa
Fig 4.13(i)
4
2500
2000
1500
1000
500
0
0
1
2
3
4
5
strain in %
6
7
0
1
2
3
4
strain in %
Fig 4.13(iii)
6
7
Fig 4.13(iv)
60 days curing
4000
stress in kPa
5
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
2000
1000
0
0
1
2
3 % 4
strain
in
5
6
7
Fig 4.13(v)
Fig 4.13 (i)-4.13(v): Stress~strain curve of stabilized fly ash prepared at compactive energy of
595 kJ/m3 and cured at 45°C temperature (sealed samples)
47 | P a g e
RESULTS AND DISCUSSION
0 days curing
800
600
400
200
3000
2000
1000
0
0
1
2 strain
3 in4 % 5
6
FA+0%L
FA+2%L
FA+4%L
FA+8%L
4000
stress in kPa
1000
stress in kPa
7 days curing
FA+0%L
FA+2%L
FA+4%L
0
7
0
1
strain
2
3in % 4
15 days curing
4000
3500
3000
2500
2000
1500
1000
500
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
1
6
7
Fig.4.14(ii)
2
3
4
strain in %
5
6
30 days curing
stress in kPa
stress in kPa
Fig 4.14(i)
5
4000
3500
3000
2500
2000
1500
1000
500
0
7
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
Fig 4.14(iii)
1
2
3
strain in %
4
5
6
7
Fig.4.14(iv)
60 days curing
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
stress in kPa
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
1
2
3
4
strain in %
5
6
7
Fig 4.14(v)
Fig 4.14 (i)-fig.4.14(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 2483 kJ/m3 and cured at 45°C temperature (sealed samples)
48 | P a g e
RESULTS AND DISCUSSION
0 days curing
stress in kPa
1000
800
600
400
7 days curing
4000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
3000
stress in kPa
FA+0%L
FA+2%L
FA+4%L
FA+8%L
200
2000
1000
0
0
0
1
2strain
3 in
4 %5
6
0
7
1
2
3
4
strain in %
Fig 4.15(i)
6
7
Fig 4.15(ii)
15 days curing
6000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
4000
30 days curing
6000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
5000
stress in kPa
5000
stress in kPa
5
3000
2000
1000
4000
3000
2000
1000
0
0
0
1
2strain
3 in %
4
5
6
0
7
1
Fig 4.15(iii)
2
3
4
5
strain in %
6
7
Fig 4.15(iv)
60 days curing
8000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
6000
4000
2000
0
0
1
2
3
4
5
strain in %
6
7
Fig 4.15(v)
Fig 4.15 (i)- Fig4.15.(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 2483 kJ/m3 and cured at 45°C temperature (unsealed samples)
49 | P a g e
RESULTS AND DISCUSSION
0 days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
stress in kPa
400
300
200
7 days curing
5000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
4000
stress in kPa
500
3000
2000
1000
100
0
0
0
1
2
3
4
strain in %
5
6
0
7
1
5
6
7
Fig 4.16(ii)
15 days curing
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
stress in kPa
stress in kPa
Fig 4.16(i)
2
3
4
strain in %
6000
30 days curing
5000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
4000
3000
2000
1000
0
0
1
2
3
4
5
strain in %
6
7
0
1
stress in kPa
Fig 4.16(iii)
2
3
4
5
strain in %
6
7
Fig 4.16(iv)
7000
60 days curing
6000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
5000
4000
3000
2000
1000
0
0
1
2
3
4
5
strain in %
6
7
Fig 4.16(v)
Fig 4.16 (i)-Fig4.16(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 595 kJ/m3 and cured at 90°C temperature (sealed samples)
50 | P a g e
RESULTS AND DISCUSSION
0 days curing
stress in kPa
1000
800
600
400
7 days curing
8000
stress in kPa
FA+0%L
FA+2%L
FA+4%L
FA+8%L
200
FA+0%L
FA+2%L
FA+4%L
FA+8%L
6000
4000
2000
0
0
0
1
2 strain
3 in4 % 5
6
0
7
1 strain
2 in3% 4
Fig 4.17(i)
15 days curing
stress in kPa
7
6000
4000
2000
0
2 3 4
strain in %
5
6
30 days curing
stress in kPa
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
1
6
Fig 4.17(ii)
8000
0
5
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
7
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
1
2
3
4
strain in %
Fig 4.17(iii)
5
6
7
Fig 4.17(iv)
60 days curing
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
10000
stress in kPa
8000
6000
4000
2000
0
0
1
2
3
4
strain in %
5
6
7
Fig 4.17(v)
Fig 4.17 (i)-Fig.4.17(v): Stress~strain curve of stabilized fly ash prepared at compactive energy
of 2483 kJ/m3 and cured at 90°C temperature (sealed samples)
51 | P a g e
RESULTS AND DISCUSSION
0 days curing
stress in kPa
stress in kPa
500
7 days curing
8000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
1000
FA+0%L
FA+2%L
FA+4%L
FA+8%L
6000
4000
2000
0
0
0
1
2strain
3 in
4 %5
6
0
7
1
2 3 in4% 5
strain
Fig 4.18(i)
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
6000
4000
2000
30 days curing
10000
stress in kPa
stress in kPa
7
Fig 4.17(ii)
15 days curing
8000
6
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
8000
6000
4000
2000
0
0
0
1
2strain3 in %4
5
6
7
0
1
Fig 4.18(iii)
6
7
Fig 4.18(iv)
60 days curing
15000
stress in kPa
2 strain
3 in4 % 5
FA+0%L
FA+2%L
FA+4%L
10000
5000
0
0
1
2 strain
3 in %
4
5
6
7
Fig 4.18(v)
Fig 4.18(i)-Fig 4.18(v):Stress~strain curve of stabilized fly ash prepared at compactive energy of
2483 kJ/m3 and cured at temperature 90°C (unsealed samples)
From the above graphs it is visible that the failure stresses of lime stabilized samples, compacted
with greater compaction energies, are higher than the samples compacted with lower compaction
energy. The failure strains vary from a value of 2 to 3.5 %, indicating brittle failures in the
specimen. Increase in curing period of lime treated fly ash specimen shows improvement in the
52 | P a g e
RESULTS AND DISCUSSION
UCS value. But with smaller amount of lime that is 1%-2% the strength improvement is
practically negligible, even if cured for long time.
3000
FA+0%L
UCS in kPa
2500
FA+2%L
2000
FA+4%L
1500
FA+8%L
1000
FA+12%L
500
0
0
7
15
30
Curing period in days
60
Fig 4.19 (i): Curing period~unconfined compressive strength curve prepared at compactive
energy 595kJ/m3 and cured at 10°C temperature (sealed samples)
UCS in kPa
4000
FA+0%L
3000
FA+2%L
2000
FA+4%L
FA+8%L
1000
FA+12%L
0
0
7
15
30
curing period in days
60
Fig 4.19(ii) Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 10°C temperature (sealed samples)
5000
FA+0%L
UCS in kPa
4000
FA+2%L
3000
FA+4%L
2000
FA+8%L
1000
FA+12%L
0
0
7
15
30
curing period in days
60
Fig 4.19(iii) Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3and cured at 10°C temperature (unsealed samples)
53 | P a g e
UCS ,in kPa
RESULTS AND DISCUSSION
3000
0 days
2500
7 days
2000
15 days
1500
30 days
1000
60 days
500
0
0
5
lime content in %
10
15
UCS in kPa
Fig 4.20(i): Lime content vs. unconfined compressive strength curve at compactive energy
593kJ/m3at temperature 10°C (sealed samples)
4000
3500
3000
2500
2000
1500
1000
500
0
0 days
7 days
15 days
30 days
60 days
0
5
10
lime content in %
15
Fig 4.20(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 10°C (sealed samples)
3000
UCS in kPa
2500
2000
0 days
1500
7 days
15 days
1000
30 days
500
60 days
0
0
5
10
lime content in %
15
Fig 4.20(iii) Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 10°C (unsealed samples)
54 | P a g e
UCS in kPa
RESULTS AND DISCUSSION
3500
3000
2500
2000
1500
1000
500
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
7
15
30
60
Curing period in days
Fig 4.21(i): Curing period~unconfined compressive strength curve prepared at compactive
energy 595kJ/m3 and cured at 25°C temperature (sealed samples)
5000
UCS in kPa
4000
FA+0%L
3000
FA+2%L
2000
FA+4%L
1000
FA+8%L
FA+12%L
0
0
7
15
30
curing period in days
60
Fig 4.21(ii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 25°C temperature (sealed samples)
UCS in kPa
5000
4000
FA+0%L
3000
FA+2%L
2000
FA+4%L
FA+8%L
1000
FA+12%L
0
0
7
15
30
60
curing period in days
Fig 4.21(iii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 25°C temperature (unsealed samples)
55 | P a g e
RESULTS AND DISCUSSION
UCS in kPa
3500
3000
0 days
2500
7 days
2000
15 days
1500
30 days
1000
60 days
500
0
0
5 content in % 10
lime
15
Fig 4.22(i): Lime content vs. unconfined compressive strength curve at compactive energy
595kJ/m3at temperature 25°C (sealed samples)
5000
UCS in kPa
4000
0 days
3000
7 days
2000
15 days
30 days
1000
60 days
0
0
5
10
lime content in %
15
Fig 4.22(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 25°C (sealed samples)
5000
UCS in kPa
4000
0 days
3000
7 days
2000
15 days
30 days
1000
60 days
0
0
5
10
15
lime content in%
Fig 4.22(iii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 25°C (unsealed samples)
56 | P a g e
RESULTS AND DISCUSSION
UCS in kPa
4000
FA+0%L
3000
FA+2%L
2000
FA+4%L
1000
FA+8%L
FA+12%L
0
0
7
15
30
Curing period in days
60
UCS in kPa
Fig 4.23(i) Curing period~unconfined compressive strength curve prepared at compactive energy
595kJ/m3 and cured at 45°C temperature (sealed samples)
5000
FA+0%L
4000
FA+2%L
3000
FA+4%L
2000
FA+8%L
1000
FA+12%L
0
0
7
15
30
curing period in days
60
Fig 4.23(ii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 45°C temperature (sealed samples)
UCS in kPa
8000
6000
FA+0%L
FA+2%L
4000
FA+4%L
2000
FA+8%L
FA+12%L
0
0
7
15
30
curing period in days
60
Fig 4.23(iii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 45°C temperature (unsealed samples)
57 | P a g e
RESULTS AND DISCUSSION
UCS in kPa
4000
3000
0 days
7 days
15 days
30 days
60 days
2000
1000
0
0
5
10
lime content in%
15
Fig 4.24(i): Lime content vs. unconfined compressive strength curve at compactive energy
595kJ/m3at temperature 45°C (sealed samples)
UCS in kPa
5000
4000
0 days
7 days
15 days
30 days
60 days
3000
2000
1000
0
0
5
10
lime content in%
15
Fig 4.24(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 45°C (sealed samples)
8000
0 days
7 days
15 days
30 days
60 days
UCS in kPa
6000
4000
2000
0
0
5
10
lime content in%
15
Fig 4.24(iii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 45°C (unsealed samples)
58 | P a g e
UCS in kPa
RESULTS AND DISCUSSION
7000
6000
5000
4000
3000
2000
1000
0
FA+0%L
FA+2%L
FA+4%L
FA+8%L
FA+12%L
0
7
15
30
Curing period in days
60
Fig 4.25(i): Curing period~unconfined compressive strength curve prepared at compactive
energy 595kJ/m3 and cured at 90°C temperature (sealed samples)
UCS in kPa
10000
8000
FA+0%L
6000
FA+2%L
4000
FA+4%L
FA+8%L
2000
FA+12%L
0
0
7
15
30
curing period in days
60
Fig 4.25(ii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 90°C temperature (sealed samples)
12000
FA+0%L
UCS in kPa
10000
FA+2%L
8000
FA+4%L
6000
FA+8%L
4000
FA+12%L
2000
0
0
7
15
30
60
curing period in days
Fig 4.25(iii): Curing period~unconfined compressive strength curve prepared at compactive
energy 2483kJ/m3 and cured at 0°C temperature (unsealed samples)
59 | P a g e
UCS in kPa
RESULTS AND DISCUSSION
7000
6000
5000
4000
3000
2000
1000
0
0 days
7 days
15 days
30 days
60 days
0
5
10
15
lime content in%
Fig 4.26(i): Lime content vs. unconfined compressive strength curve at compactive energy
595kJ/m3at temperature 90°C (unsealed samples)
10000
0 days
7 days
15 days
30 days
60 days
UCS in kPa
8000
6000
4000
2000
0
0
5
10
lime content in%
15
Fig 4.26(ii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 90°C (sealed samples)
12000
0 days
7 days
15 days
30 days
60 days
UCS in kPa
10000
8000
6000
4000
2000
0
0
5
10
lime content in%
15
Fig 4.26(iii): Lime content vs. unconfined compressive strength curve at compactive energy
2483kJ/m3at temperature 90°C (unsealed samples)
60 | P a g e
UCS in kPa
RESULTS AND DISCUSSION
400
350
300
250
200
150
100
0 days
7 days
15 days
30 days
60 days
0
25
50
75
curing temperature in°C
100
Fig 4.27(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 0% lime(sealed samples)
UCS in kPa
700
0 days
7 days
15 days
30 days
60 days
600
500
400
300
0
25
50
75
curing temperature in°C
100
UCS in kPa
Fig 4.27(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3 for 0% lime(sealed samples)
650
600
550
500
450
400
350
300
0 days
7 days
15 days
30 days
60 days
0
25
50
75
curing temperature in°C
100
Fig 4.27(iii) Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 0% lime(unsealed samples)
61 | P a g e
RESULTS AND DISCUSSION
500
UCS in kPa
0 days
400
7 days
300
15 days
30 days
200
60 days
100
0
25
50
75
curing temperature in°C
100
UCS in kPa
Fig 4.28(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 2% lime(sealed samples)
1000
900
800
700
600
500
400
300
0 days
7 days
15 days
30 days
60 days
0
25
50
75
curing temperature in°C
100
Fig 4.28(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 2% lime(sealed samples)
UCS in kPa
1100
900
0 days
700
7 days
15 days
500
30 days
60 days
300
0
25
50
75
curing temperature in°C
100
Fig 4.28(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 2% lime(unsealed samples)
62 | P a g e
RESULTS AND DISCUSSION
900
UCS in kPa
0 days
700
7 days
15 days
500
30 days
300
60 days
100
0
25
50
75
100
curing temperature in°C
Fig 4.29(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 4% lime(sealed samples)
UCS in kPa
2300
0 days
1800
7 days
1300
15 days
30 days
800
60 days
300
0
25
50
75
curing temperature in°C
100
Fig 4.29(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 4% lime(sealed samples)
2300
UCS in kPa
0 days
7 days
1800
15 days
1300
30 days
60 days
800
300
0
25
50
75
100
curing temperature in°C
Fig 4.29(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 4% lime(unsealed samples)
63 | P a g e
RESULTS AND DISCUSSION
2600
0 days
2100
UCS in kPa
7 days
1600
15 days
1100
30 days
600
60 days
100
0
25
50
75
curing temperature in°C
100
Fig 4.30(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 8% lime(sealed samples)
6300
UCS in kPa
5300
0 days
4300
7 days
3300
15 days
30 days
2300
60 days
1300
300
0
25
50
75
curing temperature in°C
100
Fig 4.30(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 8% lime(sealed samples)
6300
UCS in kPa
5300
4300
0 days
3300
7 days
2300
15 days
1300
30 days
60 days
300
0
25
50
75
100
curing temperature in°C
Fig 4.30(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 8% lime(sealed samples)
64 | P a g e
UCS in kPa
RESULTS AND DISCUSSION
7100
6100
5100
4100
3100
2100
1100
100
0 days
7 days
15 days
30 days
60 days
0
25
50
75
100
curing temperature in°C
UCS in kPa
Fig 4.31(i): Temperature vs. unconfined compressive strength curve at compactive energy
595kJ/m3for 12% lime(sealed samples)
10300
0 days
8300
7 days
6300
15 days
4300
30 days
2300
60 days
300
0
25
50
75
100
curing temperature in°C
Fig 4.31(ii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 12% lime(sealed samples)
UCS in kPa
10300
8300
0 days
6300
7 days
4300
15 days
2300
30 days
300
60 days
0
25
50
75
100
curing temperature in°C
Fig 4.31(iii): Temperature vs. unconfined compressive strength curve at compactive energy
2483kJ/m3for 12% lime(unsealed samples)
65 | P a g e
RESULTS AND DISCUSSION
4.3.3 Determination of CBR value
CBR-test was conducted to characterize the strength and the bearing capacity of the fly ash.
Toth et al. reported the CBR values of coal ashes to vary between 6.8 and 13.5% for soaked
condition, and 10.8 and 15.4% for unsoaked condition. The typical CBR value of Badarpur coal
ashes tested under soaked and unsoaked conditions reported by Pandian (2004). Basically the
unsoaked CBR value is more than soaked CBR value. CBR values under soaked conditions
would always give a highly conservative value for design.CBR value increases with increase in
compaction energy. The soaked CBR value of Fly ash is relatively low ranging from 1.3%to
5.8% as compaction energy increases from 595 to 2483 kJ/m3. However Lime treated fly ash has
comparatively higher CBR value reaching a value of 44.2% at lime content of 10%.when the
sample subjected to a curing period of 26 days and a soaking period of 4 days, CBR value
considerably increases due to pozzolanic reaction of lime. This is mainly because fly ash, a finegrained material, when placed at 95% of Proctor maximum dry density and corresponding water
content, exhibits capillary forces, in addition to friction resisting the penetration of the plunger
and thus high values of CBR are obtained. On the contrary, when the same fly ash samples are
soaked for 24 h maintaining the same placement conditions, they exhibited very low values of
CBR. This can be attributed to the destruction of capillary forces under soaked conditions. The
load Vs penetration curve of lime treated fly ash with 7days and 30 days cured samples are
shown below.
66 | P a g e
RESULTS AND DISCUSSION
18
16
14
12
10
8
6
4
2
0
load in kN
0%l
2%l
4%l
8%l
12%
0
2.5
5
7.5
10
penetration in mm
12.5
15
Fig.4.32(i) Load vs penetration curve for 7days soaked CBR at 595kJ/m³
40
35
30
25
20
15
10
5
0
load in kN
0%l
2%l
4%l
8%l
12%
0
2.5
5
7.5
10
penetration in mm
12.5
15
Fig 4.32(ii) Load vs penetration curve for 7days soaked CBR at 2483kJ/m³
60
50
40
load in kN
0%l
2%l
4%l
8%l
12%
30
20
10
0
0
2.5
5
7.5
10
penetration in mm
12.5
15
Fig 4.32(iii) Load vs penetration curve for 30days soaked CBR at 595kJ/m³
67 | P a g e
RESULTS AND DISCUSSION
100
load in kN
80
60
0%l
2%l
4%l
8%l
12%
40
20
0
0
2.5
5
7.5
10
penetration in mm
12.5
15
Fig 4.32(iv) Load vs penetration curve for 30days soaked CBR at 2483kJ/m³
25
20
load in kN
15
0%l
2%l
4%l
8%l
12%
10
5
0
0
2.5
5
7.5
10
penetration in mm
12.5
15
Fig 4.32(v) Load vs penetration curve for 7days unsoaked CBR at 595kJ/m³
50
load in kN
40
30
0%l
2%l
4%l
8%l
12%
20
10
0
0
2.5
5
7.5
10
penetration in mm
12.5
15
Fig 4.32(vi) Load vs penetration curve for 7days unsoaked CBR at 2483kJ/m³
68 | P a g e
RESULTS AND DISCUSSION
60
50
load in kN
40
0%l
30
2%l
4%l
20
8%l
12%
10
0
0
2.5
5
7.5
10
12.5
15
penetration in mm
Fig 4.32(vii) Load vs penetration curve for 30days unsoaked CBR at 595kJ/m³
100
90
load in kN
80
70
0%l
60
2%l
50
4%l
40
8%l
30
12%
20
10
0
0
2.5
5
7.5
10
12.5
15
penetration in mm
Fig 4.32(viii) Load vs penetration curve for 30days unsoaked CBR at 2483kJ/m³
69 | P a g e
RESULTS AND DISCUSSION
120
80
CBR in %
CBR in %
100
593 kJ/m³
60
2483 kJ/m³
40
20
0
0
2
160
140
120
100
80
60
40
20
0
4 6 8 10 12 14
lime content in %
593 kJ/m³
2483 kJ/m³
0
2
4 6 8 10 12 14
lime content in %
Fig 4.33(i)
Fig 4.33(ii)
Fig 4.33(i)-4.33(ii) variation of soaked and unsoaked CBR with different lime content for 7days
curing period
300
350
250
300
200
250
CBR in %
593 kJ/m³
100
2483 kJ/m³
50
0
CBR in %
200
150
593 kJ/m³
150
100
2483 kJ/m³
50
0
0
2
4
6
8
10 12 14
lime content in %
Fig 4.33(i)
0
2
4
6
8
10 12 14
lime content in %
Fig 4.33(ii)
Fig 4.34(i)-4.34(ii) variation of soaked and unsoaked CBR with different lime content for 30days
curing period
This graph shows the variation of CBR value due to increase in lime content and curing period
with 595 kJ/m3 to 2483kJ/m3 of compactive energy. And it is clearly visible that unsoaked and
soaked CBR value of untreated flyash give lesser CBR value when cured for 7days and with
curing period increase up to 30 days these values are slightly increased due to presence of some
short of cementing material (free lime).And unsoaked and soaked CBR values are found to
70 | P a g e
RESULTS AND DISCUSSION
increase with lime beyond 4% which gives marginal strength. This trend is observed for
specimens cured for 7days. However specimens cured for 30 days showed a continuous increase
in CBR value. So for better strength higher doses of lime treatment also needed. Test result
showed a great variation between unsoaked and soaked CBR values for untreated flyash or
flyash treated with low percentage of lime but this difference is reduced when the samples are
stabilized with higher percentage of lime.
4.3.4 Permeability characteristics
Variations of Co-efficient of permeability with lime content and curing period are given in table
3.16. Permeabilty decreases with increase in compactive energy. At compaction energy of 2483
kJ/m3 the co-efficient of permeability vary from 3.91×10-5cm/sec for untreated fly ash to
-5
0.474×10 cm/sec for fly ash treated with 12% lime with 7 days curing. Effect of curing period
triggered with the addition of lime result pozzolanic reaction occurs which gives closer packing
of particles. Silicon oxide and alumina oxide of fly ash react with lime which generates
cementitious gel (CSH) that bind the particles together blocking of the flow paths thus reducing
the value of coefficient of permeability. Permeability decreases with increase in compactive
energy, lime content or curing period.
71 | P a g e
CONCLUSION
CONCLUSIONS AND FURTHER WORK
5.1
Conclusions
Experiments are carried out to investigate strength properties of lime treated flyash. The effects
of lime content, curing period and curing temperature on the strength properties are investigated.
Based on the experimental investigations the following main conclusions are arrived at:
 The fly ash shows uniform gradation of particles having most of the grains is of fine sand
to silt size. The percentage of flyash passing through 75μ sieve was found to be 88%.
Coefficient of uniformity (Cu) and coefficient of curvature (Cc) for flyash was found to
be 5.67 & 1.25 respectively, indicating that it is a uniformly graded material..
 Dry density of compacted specimens is found to change from 1.12 to 1.236 g/ccwith
change in compaction energy from 595 kJ/m3to 2483 kJ/m3, whereas the OMC is found
to decrease from 40.5 to 33 %. This shows that fly ash sample responds very poorly to
the compaction energy. An addition of lime flocculates the particles which results in
decrease of dry density and increase in moisture content at a given compactive effort at
lower doses of lime. However higher lime content tends to increase the MDD value as the
specific gravity of lime is higher than that of the flyash particles.
 The failure stresses of lime stabilized samples, compacted with greater compaction
energies, are higher than the samples compacted with lower compaction energy. However
the failure strains are found to be lower for samples compacted with higher energies with
lower lime content. The failure strains vary from a value of 2 to 3.5 %, indicating brittle
failures in the specimen. A linear relationship is found to exist between the lime content
and unconfined compressive strength.
 The UCS value is found to change from 290.60 to 320.5 kPa with change in lime content
from 0 to 2% indicating that the gain in strength is not so remarkable with smaller amount of
lime that is 0 -2% the strength improvement is practically insignificant, even if cured for
long time.But a higher dose of lime that is beyond 2% enhances the unconfined strength
by many folds. This shows that about 2% of lime is used for colloidal type of reaction
and lime in excess to this amount is utilized for pozzolanic reaction and increase in
strength.
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CONCLUSION

Increase in curing period of lime treated fly ash specimen shows improvement in the
UCS and CBR value. But with smaller amount of lime that is 1%-2% the strength
improvement is practically negligible, even if cured for long time. This is similar to the
colloidal reaction with lime, which is mainly responsible in modifying the physical
properties not the mechanical strength. With increased lime content the pozzolanic
reaction peaks up producing adequate amount of cementitious compounds leading to
visible increase in strength. As the lime percentage increases this facilitates the
pozzolanic reaction that form cementitious gel that binds the particles. The process of
pozzolanic reaction is improved with curing period which results higher strength.
 Curing temperature is found to influence the unconfined strength of both sealed and
unsealed samples .The UCS values of flyash added with higher percentage of lime show
a remarkable increase in strength with increase curing temperature .however flyash added
with lower percentage of lime does not show this trend. This indicates that a higher
temperature favours a better pozzolanic reaction than a lower temperature .specially when
the lime content is high.
 Both unsealed and sealed samples shows almost comparable strength values when the
lime content is when the lime content is low and low curing period .Unsealed samples
with higher lime content shows an improved strength over the sealed sample at
comparable conditions. The increase in strength is remarkably high with higher curing
temperature and longer curing periods. This shows that the water added during moulding
of samples is insufficient to complete the pozzolanic reaction especially when the lime
content is more. Hence it is recommended that ash samples stabilized with higher amount
of lime should either be compacted wet of OMC or sufficient be added subsequently for
proper curing.
 The stress strain curves of lime treated flyash specimens show an increase in both the
stiffness value and failure stress with increase in lime content. However the failure strain
is found to decrease with increase in lime content. This indicates wit addition of lime the
samples became more stiff and strong where as it behaves more like a brittle material.
73 | P a g e
CONCLUSION
 The unsoaked and soaked CBR value of untreated flyash compacted with energy of
595kJ/m3 to 2483kJ/m3 are found to be 24.89% and 1.3% when cured for 7days and with
increase in curing period to 30 days these values are 26.71% and 2.5% respectively. This
indicates that CBR value of compacted ash is very susceptible to degree of saturation. A
slight increase in CBR value of virgin flyash with curing period indicates the presence of
some short of cementing material (free lime) in the sample which undergoes pozzolanic
reaction with silica and alumina present in the flyash on adding water.
 Both the unsoaked and soaked CBR values are found to increase with lime content up to
4% beyond which the increment is marginal. This trend is observed for specimens cured
for 7days. However specimens cured for 30 days showed a continuous increase in CBR
value with lime content. This indicates that the reaction of lime with flyash is slow and a
higher curing period is needed to complete the pozzolanic reaction.
 Normally 4 days soaked CBR values are used for design of flexible pavements .the CBR
test result showed a great variation between unsoaked and soaked CBR values for
untreated flyash or flyash treated with low percentage of lime .however this difference is
minimal when the samples are stabilized with higher percentage of lime. This indicates
that almost all flyash particles are cemented each other by added lime and saturation of
samples has no detrimental effect.
 Permeability decreases with increase in either compactive energy or lime content.
Permeability is basically a function of grain size and compactive effort. With increase in
lime content, pozzolanic reaction occurs which result in blocking of the flow paths thus
reducing the value of coefficient of permeability of the lime treated fly ash
specimens.sillicon oxide and alumina oxide of fly ash react with lime which generates
cementitious gel (CSH) that bind the particles together blocking of the flow paths thus
reducing the value of coefficient of permeability. Permeability decreases with increase in
compactive energy, lime content or curing period.
74 | P a g e
CONCLUSION
5.2
Future Work
For effective utilization of lime treated fly ash, some more aspects have to be investigated
 Effect of mineral and chemical admixtures like silica fume, glass powder etc
 Durability test to study the durability aspect
 Behaviors of stabilized flyash of perform study of under repeated loading
 Compressibility and Consolidation characteristics of compacted fly ash.
 Studies on microstructure and morphology and correlate this to the developed strength.
 Effectiveness of lime in controlling the leachate quality coming out of flyash.
 Liquefaction susceptibility of fly ash.
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